The following are steps specific to Solaris to reproduce the problem:
- login to GNOME 2.6
- logout
repeat that a number of times (say 10 times)

Then, the user is not able to login again with the hour glass lasting forever.
telnet to the machine and notice that gconfd is the process left from the 
previous login session and gconf-sanity-check-2 is waiting for gconfd to response.
gconfd is sitting in the middle of of signal handler but not able to response.
Like,

(dbx) where
current thread: t@1
=>[1] __lwp_park(0xcbef0000, 0x0), at 0xcc0348d0
  [2] mutex_lock_queue(0xcbef0000, 0x0, 0xcc013550), at 0xcc03067f
  [3] slow_lock(0xcc013550, 0xcbef0000), at 0xcc030e95
  [4] _ti_mutex_lock(0xcc013550), at 0xcc030f50
  [5] malloc(0x2c, 0x1, 0xcc077a25, 0xcc2ddc90, 0x0, 0x1), at 0xcbfa0b4c
  [6] standard_malloc(0x0, 0x8046ca4, 0x805a378, 0x8046d18, 0x80e9ff8, 0x0,
0xcc0988c1), at 0xcc077a38
  [7] _g_gnulib_vasprintf(0x1, 0x0, 0x8046dc0, 0x8056425), at 0xcc0988df
  [8] call_user_handler(0x1, 0x0, 0x8046dc0), at 0xcc02e9fb
  [9] sigacthandler(), at 0xcc02eb21
  ---- called from signal handler with signal 1 (SIGHUP) ------
  [10] _free_unlocked(0x84b2008), at 0xcbfa17c4
  [11] free(0x84b2008, 0xcc00f000, 0xcc077a6b, 0xcbfa1774, 0xcc013550,
0xcc0d6370), at 0xcbfa1766

Looking at the gconfd.c, it looks like within the signal handler for SIGHUP,
it calls, 
 gconf_log (GCL_INFO,
               _("Received signal %d, shutting down cleanly"), signo);

which calls dgettext (the above stack trace has dgettext removed) and in
gconf_log it calls g_strdup_vprintf() which callled malloc.

According to Richard Steven's book and also
http://www.linux.com/howtos/Secure-Programs-HOWTO/signals.shtml

it is a unsafe thing to malloc in the signal handler. I believe the
problem this is the problem I have seen.

Now, I tried very hard on a Linux box running GNOME 2.6 (JDS on SuSE), I just 
can't reproduce the problem. Now is there something specific or different on
Linux, I don't know.

When I removed the call to gconf_log under SIGHUP case, the problem goes away.
I log this bug so that some more experioence folks with signal may want to 
contributet to this.