Set is operating fine,suddenly shuts off the video and audio.

Set powers up and operates fine, then without warning, shuts off the video and audio (power stays on). Will sometimes return to normal (with a loud "pop") within a few minutes, sometimes will not come back on for hours. This is random - length of time between episodes and the time out of commission is highly variable. The manual indicates that this type of event is considered normal, but when it won't return to normal operation for hours - renders the set pretty much useless.