Tried the card in my other machine, and there it works flawless. I have also tried to make sure the video-card gets propely amount of air, and that made no changes (it was very hot when i removed it, so i thought this might be it...).
Reinstalled XP on the machine, and with fresh drivers, still the problem occurs. The only thing i can think of that has been changed since it failed, is that i now use a nvidia card. Previously i used a matrox, but this doesn't support theater view very well. I have an older ATI 7000 i may try, but this aint very good either...
I'll just have to try futher. Feel free to pop in suggestions if anyone has an idea:)