There are two things to try that I can think of. The first is to make sure that you are using the latest drivers for your graphics card from ATI. If that doesn't fix the problem, try the latest drivers from the card manufacturer, even if they are quite old. The driver from the card manufacturer has been tested while newer drivers have not. There may be an incompatibility with your card and the newer driver (I've had this happen to me).
~jr
http://www.johnrofrano.com
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