A strange issue has developed on my DRT400. The picture has blocks and the sound is "popping" (high pitched distortion) when playing back DVD's. It occurs with every DVD I have tried whether commercial or homemade. Everything else works fine. Recorded shows playback properly and I can even burn discs. It is striclty an issue during playback of DVD's. I have tried rebooting several times to no avail. Anybody have a similar problem or have any suggestions?