Well, occasionaly - and I've seen this ~2-3 times in the last few days, [
doing a scad of switching between X sessions and odd things ] I've got
un-repeatable lockups in this method. ie. despite it being a simple linked
list traversal it hangs in there, belts around the loop and finally dies [
presumably of a lack of memory ].

I wouldn't mind that, but often it seems to do it with an active grab that
scuppers trying to use X ;-) it's not clear how that could happen precicely.

Here's how it looks:

(gdb) bt

+ Trace 18973

Run till exit from #0  chunk_alloc (ar_ptr=0x4085e520, nb=1032)
    at malloc.c:3076
[Switching to Thread 1024 (LWP 10789)]
0x407ac02c in __libc_malloc (bytes=1024) at malloc.c:2811
2811    in malloc.c
Value returned is $1 = 0x27356e80
(gdb) finish
Run till exit from #0  0x407ac02c in __libc_malloc (bytes=1024)
    at malloc.c:2811
g_malloc (n_bytes=1024) at gmem.c:138
138     gmem.c: No such file or directory.
        in gmem.c
Value returned is $2 = (void *) 0x27356e88
(gdb) finish
Run till exit from #0  g_malloc (n_bytes=1024) at gmem.c:138
g_mem_chunk_alloc (mem_chunk=0x80a3658) at gmem.c:845
845     in gmem.c
Value returned is $3 = 0x27356e88
(gdb) finish
Run till exit from #0  g_mem_chunk_alloc (mem_chunk=0x80a3658)
    at gmem.c:845
0x406d2159 in g_slist_prepend (list=0x27356e78, data=0x82b80f0)
    at gslist.c:124
124     gslist.c: No such file or directory.
        in gslist.c
Value returned is $4 = 0x27356ea0
(gdb) finish
Run till exit from #0  0x406d2159 in g_slist_prepend (list=0x27356e78, 
    data=0x82b80f0) at gslist.c:124
0x4038825e in _gtk_key_hash_lookup (key_hash=0x8277d00, 
    hardware_keycode=9, state=0, group=0) at gtkkeyhash.c:307
307     gtkkeyhash.c: No such file or directory.
        in gtkkeyhash.c
Value returned is $5 = (GSList *) 0x27356ea0
(gdb) finish
Run till exit from #0  0x4038825e in _gtk_key_hash_lookup (
    key_hash=0x8277d00, hardware_keycode=9, state=0, group=0)
    at gtkkeyhash.c:307

[1]+  Stopped                 gdb gnome-panel-2 10789