I have recently reinstalled Ubuntu 12.04 and replaced hard drives and video cards (both nvidia) but changed drivers as I went from a 7600gt with the 173 driver to GT 640 with 310 driver. I had some success before (only HD videos would cause this issue) and now it is easily repeatable for me regardless of other circumstances.
- Open browser of choice (tested Opera, Chromium, Firefox, Chrome) to flash content
- Play flash content in full screen
- Watch PC shut off from failure
I can play Team Fortress 2 in HD 1080p. I can watch 1080p content from enormous MKV files or HTML5 from Youtube. I can play flash content in 720p from a VM on the PC and not have any issues so I don't think it is a power supply issue or a PC hardware issue.
However, something is amiss and I cannot find this issue anywhere. Help would be appreciated. It is something that (while it can be lived with) is annoying to say the least.