I'm messing around with my onboard intel G965 graphics on a DG965OT motherboard. I've had problems with video while compiz is on. I found that adding this line to xorg.conf (under the device section) fixed the problem:
Option "AccelMethod" "EXA"
The default acceleration is XXA which is older and not quite as capable. Video works now, though HDTV is a little to slow when using Compiz. My problem now is that there are some artifacts around all of my open windows. It's supposed to look like the shading from the top windows onto the lower ones.
Anyway, hopefully this information will be useful to someone else. Please share your experiences.