After doing a bit more testing using 295.53 in ubuntu 12.04 I can say that, for me at least, this issue is invariably linked to dpms. On a fresh install I can work for hours without any display artifacts, but as soon as I've stepped away for a bit and dpms has kicked in to turn off the display (which fails for the NVS 3100M in the 295 series), the artifacts start occurring. I therefore think this problem is related to bug 938124 described in this thread: http://www.nvnews.net/vbulletin/show....php?p=2552723
. Perhaps the failure to properly turn off the screen somehow triggers this bug? New bug report for 295.53 is attached.