Avast 6.0.1000 conflicting with ATI video card?

Hello, how are you all?

I was using Avast free 6.0.1000 with Windows XP SP3 up to date, when I decided to update my ATI driver from 10.4 to 10.8.

Now my PC doesn’t initialize Windows, but the Linux Ubuntu works perfectly on same computer. When I uninstalled Avast, my Windows was back in the game.

Any ideas please? I read that there are some conflict with Catalyst and the new beta, but nothing concerning stable Avast.

My pc: E2500 2Gb Ram, ATI card HD 4670.