Sega Genesis/CD games on new HDTVs.

I recently just bought a new LCD television, it has all of that HDTV stuff, and works great with every system I own, but I cannot get it to work with my Sega Genesis/CD.

for example; I started Snatcher for my Sega CD and it went through all of the Sega CD loading screens, and right up to the title of the game, and then the screen went black, and sat on the input channel, so I tried with just a Genesis game (castlevania bloodlines) and it went through the intro, title screen and character select, but once the game play started, the same thing happened, the screen went black. I tried with both my RF cables and my AV cables, but there was no difference.

The only thing that I noticed, was that if I switched channels and then switched back to the input channel, I would get about five seconds of gameplay, then it would cut out again, so the games aren't freezing.

If anyone knows anything about this problem, or has a solution or at least an explaination, that would be great. Thanks.

Cheers.