Overclocking is not an issue for me either. Neither my computer nor video card is overclocked. I don't like to run the stock ATI drivers because they are bloated .net ware. But I'll try them to see what happens.
Splash Damage (ironic considering the patch they released) has already admitted there is a problem:
Unfortunately, the FPS drop - which I have no idea if it's related to this issue or not because alot of nvidia users are complaining about the fps drop as well on the forums - makes the game virtually unplayable for me.If you have an ATI card and are crashing to the desktop when you try to join a server or load a map, please do the following:
Disable Triple Buffering in the ATI Control panel.
This should solve the crash problem and allow you to play while we work with ATI to fully resolve the issue.
It's basically just a waiting game until they fix it.