Comment 9 for bug 145015

It happened to me again this evening. Here's some stuff from /var/log

/var/log/messages syslog and user.log:
21:04:44 localhost gconfd (pt-5429): Received signal 15, shutting down cleanly
21:04:53 localhost gconfd (pt-5429): Exiting

auth.log:
21:04:51 localhost gdm[4876]: (pam_unix) session closed for user pt

daemon.log:
21:04:53 localhost gdm[4876]: Error reinitilizing server

Xorg.0.log:
Fatal server error: Caught signal 4. Server aborting

This was preceded by the following backtrace:
0: /usr/bin/X(xf86SigHandler+0x86) [0x80b4b06]
1: [0xffffe420]
2: /usr/lib/xorg/modules/extensions/libGLcore.so(_swrast_Triangle+0x2d) [0xb7b5b77d]
3: /usr/lib/xorg/modules/extensions/libGLcore.so [0xb7b9bae5]
4: /usr/lib/xorg/modules/extensions/libGLcore.so [0xb7bb325f]
5: /usr/lib/xorg/modules/extensions/libGLcore.so [0xb7bb45ab]
6: /usr/lib/xorg/modules/extensions/libGLcore.so(_tnl_run_pipeline+0x16e) [0xb7ba24b7]
7: /usr/lib/xorg/modules/extensions/libGLcore.so(_tnl_playback_vertex_list+0x4cc) [0xb7ba8c3c]
8: /usr/lib/xorg/modules/extensions/libGLcore.so [0xb7ac5872]
9: /usr/lib/xorg/modules/extensions/libGLcore.so(_mesa_CallList+0x47) [0xb7ac5d07]
10: /usr/lib/xorg/modules/extensions/libGLcore.so(glCallList+0x23) [0xb7aa9eed]
11: /usr/lib/xorg/modules/extensions/libglx.so(__glXDisp_CallList+0x1f) [0xb7cad3f3]
12: /usr/lib/xorg/modules/extensions/libglx.so(__glXRender+0xd0) [0xb7cc573f]
13: /usr/lib/xorg/modules/extensions/libglx.so [0xb7cc848d]
14: /usr/bin/X(Dispatch+0x19e) [0x8085d86]
15: /usr/bin/X(main+0x47c) [0x806e108]
16: /lib/tls/libc.so.6(__libc_start_main+0xd4) [0xb7de7ea4]
17: /usr/bin/X(FontFileCompleteXLFD+0x8d) [0x806d671]

Hope this helps a bit.