5770 - cannot play video files

[baguette]

I just purchased Sapphire 5770 graphics card, or actually mobo, graphics card, processor and new memory modules.
Everything is working quite fine except two things:

1. I'm having the inflated cursor issue, it's not a big deal as it's a common issue and will be cleared with new drivers in the future.

2. Every time I try to play any video file (in whatever program), after about 10 seconds my screen goes black, come back again, flickers and the whole computer comes unresponsive. I can move the mouse (with subsantial lag) but all I can do is reset the system. Needles to say, this is very frustrating.

Any ideas? Thanks for any help!

Specs:

i7-860, stock cooler & speed
Sapphire hd5770
Gigabyte p55-UD3R
2x2gb 1033MHz DDR3
Windows 7 Ultimate 64-bit

 

[baguette]

I think the problem is solved now. I updated my BIOS and it seems fine now, although I tested it only briefly. So if you happen to have this motherboard, I strongly recommend to update your bios, even if the newest bios is on beta stage.