flashing screen on sagem 45 dlp?

I have a sagem 45 dlp rear screen projection tv
it has a beautiful picture but after about 30 mins the screen starts to flash & then not long after that the whole picture turns green & then switches off, and the red light comes on as if the bulb has gone.If i leave it off for a while & turn it back on , perfect picture again can any one advise me on this one thanks baz