my X11 sessions keep aborting all of a sudden

That's a new phenomenon with openSUSE-12.1 on my ASUS notebook

NOUVEAU(0): Chipset: "NVIDIA NV98"

My /var/log/Xorg.0.log shows a Backtrace, then "Fatal server error":

Caught signal 3 (Quit). Server aborting

I found similar reports dating back to 2011, suggesting to try a new kernel. Well, I should have newer kernels.

Maybe I should give the proprietary nvidia X11 binaries a try.
I have to add the nvidia repository for that: "nVidia Graphics Drivers" – you find them within the "Community Repositories". If you search the "Software Management" for nvidia, simply choose the ones with the largest revision numbers, although they sound like they match only newer GPUs.

Update 2012-08-29:
The nvidia X11 driver seems to support the chipset:

[   693.912] (--) NV: Found NVIDIA GeForce 9300M GS at 01@00:00:0
[   693.912] (II) Loading /usr/lib/xorg/modules/drivers/nv_drv.so

Update 2012-08-30:

[  1374.741]
Backtrace:
[  1374.741] 0: /usr/bin/Xorg (xorg_backtrace+0x37) [0x80a86b7]
[  1374.741] 1: /usr/bin/Xorg (0x8048000+0x64a0a) [0x80aca0a]
[  1374.741] 2: (vdso) (__kernel_rt_sigreturn+0x0) [0xffffe40c]
[  1374.741] 3: /lib/libc.so.6 (__select+0x28) [0xb733c8d8]
[  1374.741] 4: /usr/bin/Xorg (WaitForSomething+0x18c) [0x80a5f3c]
[  1374.741] 5: /usr/bin/Xorg (0x8048000+0x2d792) [0x8075792]
[  1374.741] 6: /usr/bin/Xorg (0x8048000+0x207cc) [0x80687cc]
[  1374.741] 7: /lib/libc.so.6 (__libc_start_main+0xf3) [0xb7287003]
[  1374.741] 8: /usr/bin/Xorg (0x8048000+0x20ae1) [0x8068ae1]
[  1374.742]
Fatal server error:
[  1374.742] Caught signal 3 (Quit). Server aborting
[  1374.742]
[  1374.742]
Please consult the The X.Org Foundation support
         at http://wiki.x.org
 for help.
[  1374.742] Please also check the log file at "/var/log/Xorg.0.log" for additional information.

Seems to happen once only after cold booting the machine. With NOUVEAU and also with the nvidia proprietary drivers. "Alright".