HD 4870 problem

Just one other HD4970X2 problem thread, since i didn't manage to find anything concrete in any other thread. The card freezes up any time I start a game or a demanding application. The card is mounted on a ASUS p6delux MOBO and gets its power from a corsair 750w PSU. I run with VISTA ultimate64. Let me give you some examples of my problem:
Assassins Creed - At first it always freezes and crashed at UBI soft logo, but after I Installed some older drivers it let me watch the hole intromovie before crashing before Main Menu.
CoD World at War- Nothing really has time to happen before I got a message box saying something like " ActiveX problem check read me for info" and then crashing.
Europe Universals III - Loads as usual, but when main menu appears the card start malfunction. The monitor start searching after input, finds it, start searching again and finds it repeatedly with maybe 3-5 sec. Then it all crashes, blue screen or reboot.
The only game I actually been able to play is Hearts of Iron II. I like that game, but had some hop to play more advanced stuff on my new rig.

The temperature isn't high at all. Haven't seen it over 50-55...
So, do I have to return the card and bye gtx295 instead, or is it a solutions? Its very sad with my new rig and all...

Yes, the latest BIOS is installed. To be honest, the other to isn't anything my weak skills covers. But I'm willing to learn if you're willing to explain