3850 hangs up (reset imminent/needed)

Hey guys,

I've encountered a weird problem. I had been experiencing a lot of hang-ups and blue screens with the ati2dvag.dll. I decided to reinstall my drivers, I cleaned them with Cab/Driver Cleaner in Safe Mode and installed the newest Catalyst 9.3. The blue screens are gone now (got rid of the ati3duag bsod by installing some updates), but the hang-ups still occur while browsing the internet, for example. I experience two types of hang-ups - one is an instant freeze (restart needed or imminent), the other is my graphics card stops sending signal to the monitor (restart needed or imminent as well).

I memtested the RAM (0 errors), checked the temperatures (low), and still can't pinpoint what causes this hangs.

Nothing in my PC in overclocked or overvoltaged.

My specs

Abit VT-7
P4C 2.8GHz Northwood
Geil4x256mb DDR RAM
Sapphire Radeon 3850 512MB 256bit AGP
Topower 400W PSU
Samsung T240HD monitor
Win XP SP2 + latest updates

Any suggestions will be appreciated

Thanks

Chris