Created attachment 46907 [details]
Server log with crash info

Every now and then, the X server will crash on my machine and restart to kdm. I have never seen it happen live so far, it always happened when I was away from the machine for some time.

System is Debian unstable, xserver-xorg-core package version is 1.10.1-2, but the problem has been occuring for some months now.

In the server log, I find:

==========
failed to map pixmap: -12

Backtrace:
0: /usr/bin/X (xorg_backtrace+0x28) [0x4a38b8]
1: /usr/bin/X (0x400000+0x646e9) [0x4646e9]
2: /lib/libpthread.so.0 (0x7f45b8dd2000+0xf020) [0x7f45b8de1020]
3: /lib/libc.so.6 (0x7f45b7aed000+0x84b30) [0x7f45b7b71b30]
4: /usr/lib/xorg/modules/libexa.so (0x7f45b560b000+0x6436) [0x7f45b5611436]
5: /usr/lib/xorg/modules/libexa.so (0x7f45b560b000+0x8f92) [0x7f45b5613f92]
6: /usr/lib/xorg/modules/libexa.so (0x7f45b560b000+0x12355) [0x7f45b561d355]
7: /usr/lib/xorg/modules/libexa.so (0x7f45b560b000+0x9b31) [0x7f45b5614b31]
8: /usr/bin/X (0x400000+0xe0034) [0x4e0034]
9: /usr/bin/X (0x400000+0x2e283) [0x42e283]
10: /usr/bin/X (0x400000+0x31731) [0x431731]
11: /usr/bin/X (0x400000+0x257de) [0x4257de]
12: /lib/libc.so.6 (__libc_start_main+0xfd) [0x7f45b7b0bead]
13: /usr/bin/X (0x400000+0x25389) [0x425389]
Segmentation fault at address (nil)

Fatal server error:
Caught signal 11 (Segmentation fault). Server aborting

Please consult the The X.Org Foundation support 
         at http://wiki.x.org
 for help.

==========

A full server log is attached.