Weird Clone Monitor problem after new drivers

I have my TV connected to my PC so that I can watch movies etc through my DVD drive on the big screen. It worked fine (Monitor was set to be cloned to the TV so anytime I switched on the TV it would display my PC screen image) until I updated my drivers for my Nvidia 7800 GT. Now the clone image works until I have any video playing, in which case the TV screen shows only black in the video window. Somehow the clone function isn't picking up the moving video image.

I think its a codec/driver problem. I'm sorry I wasn't more specific but it seemed like its probably something that happens pretty frequently. Any help or guesses are greatly appreciated