Powercolor HD4850 problem, please help

[Tehshinta]

So, I got myself a new computer, and it keeps freezing when I play a video(oddly enough, never when I use videolan, but freezes when I use zoomplayer, ms classic media player), moving things from the hdd and when i'm downloading things.

The pc has NEVER crashed in far cry 2 or crysis(even not after 4-5 hours playing), only when I'm downloading something and/or watching a video in zoomplayer/ms classic player
I've tryed 2 different hdd's, run memtest for 5 hours without problems, 3 differnet windows XP (sp2, sp3 and 64) and it happens on all of them. But when I tryed anohter gpu card in the pc, it stopped freezing when downloading/watching movie.

This is what happens when it freezes:

is the graphic card defect?

any help would be much appriciated

Other speccs:
Corsair TWIN2X 6400 DDR2, 4096MB CL5,
Intel Core 2 Duo E8400 3.0GHz, Socket
Corsair Powersupply 550W Black, ATX/EPS,
MSI P45 ZILENT, P45, Socket-775, DDR2,
PowerColor Radeon HD 4850 "PCS" 512MB,
Samsung SpinPoint F1 640GB SATA2

 

[meodowla]

Videolan player works on Hardware Acceleration. I think you have problem with display driver. TRy this... Uninstall all ATi drivers from you HDD with Driver Sweaper... Install ATi dispaly driver v8.12(without Catalyst Controller). Now check if problem persists..