HD4870 cannot create Direct3D

[Kaldskryke]

I recently bought an HD4870 and for the most part it's been very pleasing.

However, occasionally I will attempt to start a game and I will get an error such as "Unable to create Direct3D."

Once this occurs I can further verify that DirectX is not working by launching dxdiag and running the Direct3D tests, which all fail.

Restarting always fixes the problem, but I have no idea what causes it. Any ideas?

I'm using cat 8.12