After playing for a few minutes (game or DVD playback) red lines start to appear across the screen.
At first it is subtle, but after 15 minutes or more it will start to flicker the whole screen with a red contrast and intermittantly go blank. Sound drops out also.
I think it is the HDMI port on the XBOX that is causing the problem.
It may be that the HDMI components are getting hot but the XBOX is in a well ventilated area.
I do not have the same problem with using another game console in the same HDMI port of my flat screen TV.