As for the GPU temperature, there is no ATI OverDrive tab in my CCC (See first attached image)
Also if it's of any help, I've always had graphics glitches as well, with any and all drivers I've used. In a game there will be small neon green and sometimes purple spots on textures, 3D models will sometimes be disfigured, and sometimes there will be flashing lines and shapes (see the black shape in the left part of the second attached image for example). I'm not terribly annoyed by it, but I didn't know if that might provide any additional hints pointing to the source of the problem.
This is why I think you have a faulty card. The type of artifacting and crashing you are having usually only occurs in overclocking/overheating scenarios. For temperature and more information try GPU-Z:
GPU-Z Video card GPU Information Utility