In the five days since I booted a 2.6.25-rc6 kernel on my development
machine, it has happened three times already that I came back to the
machine to find that the X server had exited, killing all applications
that still had a window open. This has never happened with previous
kernel versions (2.6.22.17, 2.6.24.3, 2.6.25-rc5), so I suspect some
relation to the latest rc kernel.

Syslog entries around the time of the crash (identical each time):

Mar 24 21:59:57 xenon kernel: [424469.161592] PM: Removing info for No
Bus:vcs7
Mar 24 21:59:57 xenon kernel: [424469.162591] PM: Removing info for No
Bus:vcsa7
Mar 24 21:59:57 xenon kernel: [424469.179556] uhci_hcd 0000:00:1d.1:
release dev 4 ep81-INT, period 8, phase 4, 93 us
Mar 24 21:59:57 xenon gconfd (ts-21705): Signal 15 erhalten,
ordungsgem=E4=DFes Herunterfahren
Mar 24 21:59:57 xenon gconfd (ts-21705): Beenden
Mar 24 21:59:57 xenon gdm[21341]: WARNING: gdm_slave_xioerror_handler:
Schwerwiegender X-Fehler - :0 wird neu gestartet
Mar 24 21:59:58 xenon kernel: [426716.212842] PM: Adding info for No
Bus:vcs7
Mar 24 21:59:58 xenon kernel: [426716.213300] PM: Adding info for No
Bus:vcsa7
Mar 24 21:59:58 xenon kernel: [426716.295997] PM: Removing info for No
Bus:vcs7
Mar 24 21:59:58 xenon kernel: [426716.296110] PM: Removing info for No
Bus:vcsa7
Mar 24 21:59:59 xenon kernel: [426716.434662] PM: Adding info for No
Bus:vcs7
Mar 24 21:59:59 xenon kernel: [426716.434742] PM: Adding info for No
Bus:vcsa7
Mar 24 22:00:00 xenon kernel: [426717.727427] uhci_hcd 0000:00:1d.1:
reserve dev 4 ep81-INT, period 8, phase 4, 93 us
Mar 24 22:00:00 xenon kernel: [424472.319521] uhci_hcd 0000:00:1d.1:
release dev 4 ep81-INT, period 8, phase 4, 93 us
Mar 24 22:00:00 xenon kernel: [426717.997926] uhci_hcd 0000:00:1d.1:
reserve dev 4 ep81-INT, period 8, phase 4, 93 us
Mar 24 22:00:02 xenon gconfd (root-15531): (Version 2.20.0) wird
gestartet, Prozesskennung 15531, Benutzer =BBroot=AB
Mar 24 22:00:02 xenon gconfd (root-15531): Die Adresse
=BBxml:readonly:/etc/gconf/gconf.xml.mandatory=AB wurde an der Position 0=
 zu
einer nur lesbaren Konfigurationsquelle aufgel=F6st
Mar 24 22:00:02 xenon gconfd (root-15531): Die Adresse
=BBxml:readwrite:/root/.gconf=AB wurde an der Position 1 zu einer
schreibbaren Konfigurationsquelle aufgel=F6st
Mar 24 22:00:02 xenon gconfd (root-15531): Die Adresse
=BBxml:readonly:/etc/gconf/gconf.xml.defaults=AB wurde an der Position 2 =
zu
einer nur lesbaren Konfigurationsquelle aufgel=F6st
Mar 24 22:00:02 xenon gconfd (root-15531): Die Adresse
=BBxml:readonly:/etc/gconf/gconf.xml.schemas=AB wurde an der Position 3 z=
u
einer nur lesbaren Konfigurationsquelle aufgel=F6st
Mar 24 22:00:05 xenon kernel: [426722.904631] gtk-window-deco[15527]:
segfault at 4 ip b785c98a sp bfa4d160 error 4 in
libcairo.so.2.11.5[b7852000+7c000]

(The translation of the German error message from gdm is:
"Serious X error - restarting :0"
The German language messages from gconfd are probably not important,
as they appear identically during a regular X logout/login cycle.)

I'm at a loss where to start investigating this. Bisecting appears
impractical given the error happens about every other day with no
obvious triggering condition (except me being afk for a longer time.)

Configuration: Pentium D940, 2 GB RAM, Intel 965 chipset, Matrox
G550 PCIe graphics adapter, openSUSE 10.3 32 bit install.

Ideas?

Thanks
Tilman