I have the same problem with two (very) different hardware:
An Intel based computer with an NVidia graphic card and the clased-source driver. Using a fresh install of Ubuntu 12.04. See hw1
An AMD based computer, with an AMD graphic card using the open source driver. Upgraded to precise. See hw2
I have seen the same problem on a laptop using Ubuntu oneiric.
I have the same problem with two (very) different hardware:
An Intel based computer with an NVidia graphic card and the clased-source driver. Using a fresh install of Ubuntu 12.04. See hw1
An AMD based computer, with an AMD graphic card using the open source driver. Upgraded to precise. See hw2
I have seen the same problem on a laptop using Ubuntu oneiric.