If I suspected heat issues I could place a fan at low speed pointing at the rear of such a set to give it a little boost in cooling.
Last night I unplugged it and cleaned out the back with canned air, it worked fine for the rest of the evening but this morning it did again. It started a few weeks ago but we thought it was our cable provider, we would change the channel and then back again and it was fine. Now it doesn't matter what we do, it also freezes while watching dvd's so we know its not the provider. The lamp is due to be changed, we have no green lights left. Could the lamp needing to be changed do this???