Welcome to the black triangles problem. Submit a catalyst feedback support ticket and send them screenshots and threads on this site that discuss the issue. also download PC wizard 2008 from CPUID and look under the 'video' tab, look at opengl and see if it says 'no, software' next to hardware acceleration.
Report it, when you get an automated reply check back on 'my support' and say it didn't solve the problem.
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Core 2 Duo E4300 @ 2997mhz (333x9 @1.3250v) (66.5% Overclock, stock voltage), Arctic Cooling Freezer 7 Pro, 2gb PC6400 OCZ Special Ops (5-5-5-12 @ 2.1v) @ (4-4-4-10 @ 2.0v) @ 667mhz, Gigabyte GA-965P-DS3 rev 2.0 F13 BIOS, Coolermaster iGreen 430w PSU, Sapphire X1600 pro 256mb DDR2, Samsung SpinPoint 2504C SATA 2, Samsung SH-S183A DVDRW, Vista Ultimate x64 SP1