Here is a video of the problem:
I've already replaced the DMD chip hoping that would fix it however it did not. Sad I went through all that and it didn't fix it.
I have discovered that taking the back off and pointing a small fan in the back is helping prevent it. I might just need to replace the fans.
It doesn't seem to start until the set warms up a bit so it could just be that.
I had replaced the fans only two years ago, so I didn't think they would go that soon, that was the first time I replaced them since I got the set 8/6/2005.
I also recently replaced the bulb, first with a cheaper one where the housing didn't fit right and the bulb was soldered. I made this one fit by reaming out the screw hole.
I then got a philips bulb and put it in an old housing and it is much brighter and a better picture.
The set was never turning off as if it was reaching some temperature limit.