Not sure if this will help, but ...

My paper yesterday had a few pages on the three new consoles, comparing them and giving an overview of what they offer because of the PS3 launch tomorrow. A page and a half was devoted to TVs, cabling, and what all the jargon meant. In the xbox's section it said that some TVs are touchy about accepting HD signals from some cables. While the article said that the offical cable has the best chance of working with any given TV, it did say that some rare TVs don't like it.

So if you can find a different make of cable it might be worth a try.