If you say it was working fine before, then there are a few things that could be going on. I'll assume that you've tried other DVDs (not to insult your intelligence). I suppose you could try a lens cleaner... I've never had any luck with them but you might. Have you installed any new programs that require alot of resources? That could cause the video and sound to be "choppy" (alternating off and on). That's about all I can offer. It's not much, but those are the things that I'd check first. It appears to either be a dirty lens or that your CPU is way overworked, which would cause choppy playback.