Since nvidia-340xx: randomly xserver (1.16.2) crashes on Geforce 8600GT

Since version 340 of the driver, my Desktop has become unstable. I have to deal with randomly crashes of the xserver. Sometimes the Xsystem is usable for the whole day and on other days, I’ve got a crash every five minutes. I use the latest legacy-drivers (340.58) and an actual kernel (3.17.4).

I noticed, that most of the time a crash goes together with the usage of a browser (Firefox 33.1.1, Chromium 39.0.2171.71).

I use a light kde4 (4.14.3) with enabled Desktop-Effekts on Archlinux. For now I’m testing if these crashes also occure with disabled effects.

I copied the errormessage of the xserver out of Xorg.0.log into the codeblock underneath. It would be great, if one can help me with this problem.

EDIT: I forgot to mention that I use a dual-display setup.

87.301] (EE) 
[    87.301] (EE) Backtrace:
[    87.304] (EE) 0: /usr/bin/Xorg.bin (xorg_backtrace+0x56) [0x593d36]
[    87.304] (EE) 1: /usr/bin/Xorg.bin (0x400000+0x197e89) [0x597e89]
[    87.304] (EE) 2: /usr/lib/libc.so.6 (0x7fa19df42000+0x33b20) [0x7fa19df75b20]
[    87.304] (EE) 3: /usr/lib/xorg/modules/drivers/nvidia_drv.so (0x7fa1976d0000+0x5c90d6) [0x7fa197c990d6]
[    87.304] (EE) 4: /usr/lib/xorg/modules/drivers/nvidia_drv.so (0x7fa1976d0000+0x5a75f9) [0x7fa197c775f9]
[    87.304] (EE) 5: /usr/lib/xorg/modules/drivers/nvidia_drv.so (0x7fa1976d0000+0x14bdff) [0x7fa19781bdff]
[    87.304] (EE) 6: /usr/lib/xorg/modules/drivers/nvidia_drv.so (0x7fa1976d0000+0x14d696) [0x7fa19781d696]
[    87.304] (EE) 7: /usr/lib/xorg/modules/drivers/nvidia_drv.so (0x7fa1976d0000+0x14e616) [0x7fa19781e616]
[    87.304] (EE) 8: /usr/lib/xorg/modules/drivers/nvidia_drv.so (0x7fa1976d0000+0x15007f) [0x7fa19782007f]
[    87.304] (EE) 9: /usr/lib/xorg/modules/drivers/nvidia_drv.so (0x7fa1976d0000+0x146172) [0x7fa197816172]
[    87.304] (EE) 10: /usr/lib/xorg/modules/drivers/nvidia_drv.so (0x7fa1976d0000+0x1502a1) [0x7fa1978202a1]
[    87.304] (EE) 11: /usr/lib/xorg/modules/drivers/nvidia_drv.so (0x7fa1976d0000+0x15223b) [0x7fa19782223b]
[    87.304] (EE) 12: /usr/lib/xorg/modules/drivers/nvidia_drv.so (0x7fa1976d0000+0x127b92) [0x7fa1977f7b92]
[    87.304] (EE) 13: /usr/lib/xorg/modules/drivers/nvidia_drv.so (0x7fa1976d0000+0x5933fd) [0x7fa197c633fd]
[    87.304] (EE) 14: /usr/lib/xorg/modules/extensions/libglx.so (0x7fa19aeee000+0x6853db) [0x7fa19b5733db]
[    87.304] (EE) 
[    87.304] (EE) Segmentation fault at address 0x0
[    87.304] (EE) 
Fatal server error:
[    87.304] (EE) Caught signal 11 (Segmentation fault). Server aborting
[    87.304] (EE) 
[    87.304] (EE)

nvidia-bug-report-20141202.log.gz (77.4 KB)