I just started to have an issue on my mac last week. i have a 2009 mac pro 2.66 quad core desktop and i am running snow leopard 10.6.8. my graphics card is a nvidia geforce gt 120. (i know i am out of date) while browsing and watching a video, my screen went into a bizarre frozen "stuttered or pixelated" mess. there are small bars and pieces of information repeated everywhere. if i click windows, the graphics look like a repeated trail or stuttering repeated graphics over the entire screen. I have istatpro on the widgets and have been monitoring cpu heat. usually this happens when the cpu is around or over 50 celsius i think. i do not see a heat for the graphics card. also, my mouse still moves and i have found if i move the cursor to the hot corner for my screen saver to let that run for a few seconds, usually the issue clears once i click back onto the finder and wake it up. the computer does not seem to be crashing, as applications are still fine and running once the crazy mosaic screen is gone. it has happened a few times. sometimes i cannot clear the display, so i have to unplug and restart because i cannot see any menus. with light use, or no media content, the computer seems to be fine. i have noticed some mild to moderate hanging as well while using web browsers, especially scrolling. my question is, would this most likely be a hardware issue? or is my graphics card just ready to die? are there any other concerns like a corrupt HD? i have run disk utility and HD is ok according to that. i have also run clamxav and no files were found to be corrupt.