This happened after about 30 minutes of watching a flash video in fullscreen (using Firefox): the video froze, leaving just the audio playing, and the display no longer responded to user input until I ssh’d in and killed gnome-session for the user (after which LightDM login came up and things worked again).

According to user this freezing has been occurring daily, sometimes multiple times a day, since upgrading to Precise. It never occurred with Lucid.

We’ve yet to try if using 2D desktop or disabling KMS helps.

(Apport wouldn’t send this report without me lying to it that I was referred here by tech support, but I wasn’t.)

Bug #994203 looks similar, but it’s about NV4e whereas this is an NV4c.