Seems this is a 10.6.3 problem and that I am not alone with this problem. I have now reinstalled and updated to 10.6.2 using Nv50hal and resman from 10.6.1. DVI output now works fine using DVI-HDMI cable.
I will stick with this until a solution is found in 10.6.3 (c:
Thanks for the help anyways guys!