See attached images. Anyone else seeing this problem? Initially thought it was caused by my running the Strata3D app, but it has happened without that app running. It goes away with reboot. I looked at the hole/vent on the back of the iMac and it was pretty well covered up with dust. Could my video card be over heating? I cleaned out the dust, deleted Strata and rebooted. So far it's good, but it's only been about 30 minutes. Any ideas? Thanks in advance!