Vista - DirectX problems with ATI Mobility Radeon X700 and Games

I'm running the following system:

Toshiba Satellite M70-148:
Processor: Intel Pentium M processor 2.00GHz
Memory(RAM): 1,00 GB
Primary harddisk: 93.16 GB
Graphics: ATI Mobility Radeon X700
Gaming Graphics: 256 MB Memory

Windows Vista Beta 2 Evaluation copy Build 5384.

The graphic card is running on the last ATI drives with the Catalist running.
I installed some games and always get the messege that it has a problem with
DirectX. The last one happend with Command & Conquer Generals.

The messege is:

"Please make sure you have DirectX 8.1 or higher installed. Also verify that
your video card meets the minimum requirements."

All windows programs are running well but all games have the DirectX problem.

I installed and uninstalled it some times but it didn't help.

How can i solve this problem?