Steps to produce error
From command line, either of these will fail
gst-launch filesrc location=song.mp3 ! mad ! alsasink
gst-launch filesrc location=song.flac ! flacdec ! alsasink

What actually happens:
Floating Point Exception.

Additional output captured by running gst-launch with --debug-level=5
The extra control characters appear to be color codes. It looks ok when you
`cat` the output. I wasn't sure how to strip them off. 

DEBUG (1089406594:300471) [00;01;31m     GST_STATES[00m([334m 8013[00m)
[00;01;31mgstbin.c(753):gst_bin_change_state:<pipeline0>[00m changing state of
child flacdec0 from current READY to pending PAUSED
INFO  (1089406594:300523) [00;01;31m     GST_STATES[00m([334m 8013[00m)
[00;01;31mgstelement.c(2710):gst_element_set_state:<flacdec0>[00m setting
state from READY to PAUSED
LOG   (1089406594:300579) [00;01;31m     GST_STATES[00m([334m 8013[00m)
[00;01;31mgstelement.c(2897):gst_element_change_state:<flacdec0>[00m default
handler tries setting state from READY to PAUSED 0204
DEBUG (1089406594:300630) [00;01;34m       GST_CAPS[00m([334m 8013[00m)
[00;01;34mgstelement.c(2776):gst_element_negotiate_pads:<flacdec0>[00m
negotiating pads
DEBUG (1089406594:300701) [00;01;34m       GST_CAPS[00m([334m 8013[00m)
[00;01;34mgstelement.c(2823):gst_element_negotiate_pads:<flacdec0>[00m perform
negotiate for flacdec0:src and alsasink0:sink
DEBUG (1089406594:300752) [00;01;34m       GST_CAPS[00m([334m 8013[00m)
[00;01;34mgstpad.c(2618):gst_pad_get_caps:[00m get pad caps of flacdec0:src
(0x80b8f68)
DEBUG (1089406594:300799) [00;01;34m       GST_CAPS[00m([334m 8013[00m)
[00;01;34mgstpad.c(2623):gst_pad_get_caps:[00m using pad getcaps function
DEBUG (1089406594:300869) [00;01;34m       GST_CAPS[00m([334m 8013[00m)
[00;01;34mgstpad.c(2618):gst_pad_get_caps:[00m get pad caps of alsasink0:sink
(0x8097160)
DEBUG (1089406594:300918) [00;01;34m       GST_CAPS[00m([334m 8013[00m)
[00;01;34mgstpad.c(2623):gst_pad_get_caps:[00m using pad getcaps function
LOG   (1089406594:304582) [00m           alsa[00m([334m 8013[00m)
[00mgstalsa.c(858):gst_alsa_get_caps:<alsasink0>[00m get_caps returns
audio/x-alaw, rate=(int)[ 8000, 192000 ], channels=(int)[ 1, 32 ];
audio/x-mulaw, rate=(int)[ 8000, 192000 ], channels=(int)[ 1, 32 ];
audio/x-raw-float, width=(int){ 32, 64 }, endianness=(int)1234, rate=(int)[
8000, 192000 ], channels=(int)[ 1, 32 ]; audio/x-raw-int, width=(int)16,
depth=(int)16, signed=(boolean){ false, true }, endianness=(int){ 1234, 4321 },
rate=(int)[ 8000, 192000 ], channels=(int)[ 1, 32 ]; audio/x-raw-int,
width=(int)32, depth=(int)24, signed=(boolean){ false, true }, endianness=(int){
1234, 4321 }, rate=(int)[ 8000, 192000 ], channels=(int)[ 1, 32 ];
audio/x-raw-int, width=(int)32, depth=(int)32, signed=(boolean){ false, true },
endianness=(int){ 1234, 4321 }, rate=(int)[ 8000, 192000 ], channels=(int)[ 1,
32 ]; audio/x-raw-int, width=(int)24, depth=(int)24, signed=(boolean){ false,
true }, endianness=(int){ 1234, 4321 }, rate=(int)[ 8000, 192000 ],
channels=(int)[ 1, 32 ]; audio/x-raw-int, width=(int)24, depth=(int)20,
signed=(boolean){ false, true }, endianness=(int){ 1234, 4321 }, rate=(int)[
8000, 192000 ], channels=(int)[ 1, 32 ]; audio/x-raw-int, width=(int)24,
depth=(int)18, signed=(boolean){ false, true }, endianness=(int){ 1234, 4321 },
rate=(int)[ 8000, 192000 ], channels=(int)[ 1, 32 ]; audio/x-raw-int,
width=(int)8, depth=(int)8, signed=(boolean){ true, false }, rate=(int)[ 8000,
192000 ], channels=(int)[ 1, 32 ]
DEBUG (1089406594:304828) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1370):gst_pad_link_try:[00m negotiating given
link
DEBUG (1089406594:304879) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1325):gst_pad_link_negotiate:[00m negotiating
link from pad flacdec0:src to pad alsasink0:sink
DEBUG (1089406594:304932) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1113):gst_pad_link_intersect:[00m
intersecting link from flacdec0:src to alsasink0:sink
DEBUG (1089406594:304981) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1114):gst_pad_link_intersect:[00m ... srccaps
audio/x-raw-int, endianness=(int)1234, signed=(boolean)true, width=(int)16,
depth=(int)16, rate=(int)[ 11025, 48000 ], channels=(int)[ 1, 2 ]
DEBUG (1089406594:305180) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1115):gst_pad_link_intersect:[00m ...
sinkcaps audio/x-alaw, rate=(int)[ 8000, 192000 ], channels=(int)[ 1, 32 ];
audio/x-mulaw, rate=(int)[ 8000, 192000 ], channels=(int)[ 1, 32 ];
audio/x-raw-float, width=(int){ 32, 64 }, endianness=(int)1234, rate=(int)[
8000, 192000 ], channels=(int)[ 1, 32 ]; audio/x-raw-int, width=(int)16,
depth=(int)16, signed=(boolean){ false, true }, endianness=(int){ 1234, 4321 },
rate=(int)[ 8000, 192000 ], channels=(int)[ 1, 32 ]; audio/x-raw-int,
width=(int)32, depth=(int)24, signed=(boolean){ false, true }, endianness=(int){
1234, 4321 }, rate=(int)[ 8000, 192000 ], channels=(int)[ 1, 32 ];
audio/x-raw-int, width=(int)32, depth=(int)32, signed=(boolean){ false, true },
endianness=(int){ 1234, 4321 }, rate=(int)[ 8000, 192000 ], channels=(int)[ 1,
32 ]; audio/x-raw-int, width=(int)24, depth=(int)24, signed=(boolean){ false,
true }, endianness=(int){ 1234, 4321 }, rate=(int)[ 8000, 192000 ],
channels=(int)[ 1, 32 ]; audio/x-raw-int, width=(int)24, depth=(int)20,
signed=(boolean){ false, true }, endianness=(int){ 1234, 4321 }, rate=(int)[
8000, 192000 ], channels=(int)[ 1, 32 ]; audio/x-raw-int, width=(int)24,
depth=(int)18, signed=(boolean){ false, true }, endianness=(int){ 1234, 4321 },
rate=(int)[ 8000, 192000 ], channels=(int)[ 1, 32 ]; audio/x-raw-int,
width=(int)8, depth=(int)8, signed=(boolean){ true, false }, rate=(int)[ 8000,
192000 ], channels=(int)[ 1, 32 ]
DEBUG (1089406594:305739) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1116):gst_pad_link_intersect:[00m ...
filtercaps (NULL)
DEBUG (1089406594:305892) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1128):gst_pad_link_intersect:[00m
intersection audio/x-raw-int, endianness=(int)1234, signed=(boolean)true,
width=(int)16, depth=(int)16, rate=(int)[ 11025, 48000 ], channels=(int)[ 1, 2 ]
DEBUG (1089406594:305997) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1163):gst_pad_link_fixate:[00m trying to
fixate caps audio/x-raw-int, endianness=(int)1234, signed=(boolean)true,
width=(int)16, depth=(int)16, rate=(int)[ 11025, 48000 ], channels=(int)[ 1, 2 ]
DEBUG (1089406594:306141) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1175):gst_pad_link_fixate:[00m app srcpad
signal fixated to (NULL)
DEBUG (1089406594:306205) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1180):gst_pad_link_fixate:[00m app sinkpad
signal fixated to (NULL)
DEBUG (1089406594:306257) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1191):gst_pad_link_fixate:[00m srcpad
flacdec0:src doesn't have a fixate function
DEBUG (1089406594:306437) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1200):gst_pad_link_fixate:[00m sinkpad
alsasink0:sink fixated to audio/x-raw-int, endianness=(int)1234,
signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100,
channels=(int)[ 1, 2 ]
DEBUG (1089406594:306609) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1175):gst_pad_link_fixate:[00m app srcpad
signal fixated to (NULL)
DEBUG (1089406594:306689) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1180):gst_pad_link_fixate:[00m app sinkpad
signal fixated to (NULL)
DEBUG (1089406594:306742) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1191):gst_pad_link_fixate:[00m srcpad
flacdec0:src doesn't have a fixate function
DEBUG (1089406594:306921) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1200):gst_pad_link_fixate:[00m sinkpad
alsasink0:sink fixated to audio/x-raw-int, endianness=(int)1234,
signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
DEBUG (1089406594:307113) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1339):gst_pad_link_negotiate:[00m trying to
call link function on caps audio/x-raw-int, endianness=(int)1234,
signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
DEBUG (1089406594:307224) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1263):gst_pad_link_call_link_functions:[00m
calling link function on pad flacdec0:src
DEBUG (1089406594:307275) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1279):gst_pad_link_call_link_functions:[00m
got reply 0 from link function on pad flacdec0:src
INFO  (1089406594:307324) [00;01;34m       GST_CAPS[00m([334m 8013[00m)
[00;01;34mgstpad.c(1284):gst_pad_link_call_link_functions:[00m pad
flacdec0:src doesn't accept caps audio/x-raw-int, endianness=(int)1234,
signed=(boolean)true, width=(int)16, depth=(int)16, rate=(int)44100, channels=(int)2
DEBUG (1089406594:307437) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1386):gst_pad_link_try:[00m link delayed,
replacing link caps and returning
DEBUG (1089406594:307492) [00;01;37;41m       GST_PADS[00m([334m
8013[00m) [00;01;37;41mgstpad.c(1393):gst_pad_link_try:[00m copying stuff
from oldlink
LOG   (1089406594:307577) [00;01;31m     GST_STATES[00m([334m 8013[00m)
[00;01;31mgstelement.c(2949):gst_element_change_state:<flacdec0>[00m signaling
state change from READY to PAUSED
DEBUG (1089406594:307629) [00m      scheduler[00m([334m 8013[00m)
[00mgstoptimalscheduler.c(1484):gst_opt_scheduler_state_transition:[00m
element "flacdec0" state change 516
LOG   (1089406594:307698) [00;01;31m     GST_STATES[00m([334m 8013[00m)
[00;01;31mgstbin.c(652):gst_bin_child_state_change:[00m child flacdec0 changed
state in bin pipeline0 from READY to PAUSED
DEBUG (1089406594:307760) [00;01;31m     GST_STATES[00m([334m 8013[00m)
[00;01;31mgstbin.c(781):gst_bin_change_state:[00m child 'flacdec0' changed
state to 4(PAUSED) successfully
DEBUG (1089406594:307813) [00;01;31m     GST_STATES[00m([334m 8013[00m)
[00;01;31mgstbin.c(753):gst_bin_change_state:<pipeline0>[00m changing state of
child alsasink0 from current READY to pending PAUSED
INFO  (1089406594:307866) [00;01;31m     GST_STATES[00m([334m 8013[00m)
[00;01;31mgstelement.c(2710):gst_element_set_state:<alsasink0>[00m setting
state from READY to PAUSED
INFO  (1089406594:308288) [00m           alsa[00m([334m 8013[00m)
[00mgstalsa.c(1482):gst_alsa_set_hw_params:<alsasink0>[00m Preparing format:
(none)
[Invalid UTF-8] DEBUG (1089406594:308611) \x1b[00m          
alsa\x1b[00m(\x1b[334m 8013\x1b[00m)
\x1b[00mgstalsa.c(1357):gst_alsa_hw_params_dump:<alsasink0>\x1b[00m ACCESS: 
MMAP_INTERLEAVED MMAP_NONINTERLEAVED MMAP_COMPLEX RW_INTERLEAVED RW_NONINTERLEAVED
FORMAT:  S8 U8 S16_LE S16_BE U16_LE U16_BE S24_LE S24_BE U24_LE U24_BE S32_LE
S32_BE U32_LE U32_BE FLOAT_LE FLOAT_BE FLOAT64_LE FLOAT64_BE MU_LAW A_LAW
IMA_ADPCM S24_3LE S24_3BE U24_3LE U24_3BE S20_3LE S20_3BE U20_3LE U20_3BE
S18_3LE S18_3BE U18_3LE U18_3BE
SUBFORMAT:  STD
SAMPLE_BITS: [4 64]
FRAME_BITS: [4 640000]
CHANNELS: [1 10000]
RATE: [4000 4294967295)
PERIOD_TIME: (45 92880)
PERIOD_SIZE: (0 398916563)
PERIOD_BYTES: (0 4294967295)
PERIODS: (0 4294967295]
BUFFER_TIME: [1 4294967295]
BUFFER_SIZE: [1 797831566]
BUFFER_BYTES: [1 4294967295]
TICK_TIME: 1000
){ false, true }, endianness=(int){ 1234, 4321 }, rate=(int)[ 8000, 192000 ],
channels=(int)[ 1, 32 ]; audio/x-raw-int, width=(int)24, depth=(int)24,
signed=(boolean){ false, true }, endianness=(int){ 1234, 4321 }, rate=(int)[
8000, 192000 ], channels=(int)[ 1, 32 ]; audio/x-raw-int, width=(int)24,
depth=(int)20, signed=(boolean){ false, true }, endianness=(int){ 1234,\xe1\x05
Floating Point Exception

Operating System info:
Kernel-> Gentoo-2.6.7-r8
GCC -> 3.3.3
GLIBC->2.3.3.20040420-r0
GStreamer -> 0.8.3
Plugins -> gst-plugin-alsa-0.8.2, gst-plugins-mad-0.8.2, gst-plugins-flac-0.8.2,
gst-plugins-gnomevfs-0.8.2

I can get xmms to play the same files fine. I also get a tone when I run 
gst-launch-0.8 sinesrc ! alsasink

I can provide more info to help track this down, but will probably need a
pointer as to what kind would be useful. 

Thanks,
-A