Created attachment 118460 [details]
error.gz

Bug description: When the GPU hangs, the computer stops responding to input for about 10-15 seconds, then kills the desktop and any applications running within it. The user is left at the Ubuntu login screen. When the user attempts to log back onto the desktop, the computer tries to bring up the desktop, fails, and returns to the login screen. 

System environment:
-- system architecture: i686
-- kernel version: 3.13.0-63-generic
-- Linux distribution: Ubuntu 14.04 32-bit
-- Machine or mobo model: Quanta KN1 notebook, Mobile 915GM/PM/GMS/910GML

Reproducing steps: It is unclear what causes this problem. It does not only occur when using a specific application. The periods between machine restarts and GPU hangs is seemingly random. The only consistent method known to reproduce this is to use the computer and wait for it to happen.
 
Additional info: This is a fairly low priority issue. The machine is old and not used for anything important, and the problem occurs so infrequently (days to weeks between restarts) that it has not seriously impacted its utility. 

This problem has occurred on this machine since some time in 2014 (about a year now). Prior to summer 2015, when the GPU hung, it didn't kill the desktop completely, but did kill compiz. This left windowed applications open, but without menu bars or title bars. Attempting to resurrect compiz post-crash always failed.