Comment 34 for bug 270617

Not sure if it helps at all, but there is a 3 page discussion of this bug at:
http://ubuntuforums.org/showthread.php?t=1006396

With screen grabs, and I believe some logs as well.

I've had this occur for me a well, on every 177.x version of the nVidia driver that I have run. Currently running 177.82.

The really weird thing is - it NEVER happens if I have a 2nd monitor attached, and I'm in twinview. It only every happens to me when I'm displaying on a single screen on my laptop.

Dell XPS M1710
NVidia GeForce GO 7950 GTX Card