I've had similar problems with mine recently as well, recorded UFC 71 the other night and watched it last night and every now and then the sound goes dead for about 2 seconds then when it comes back on its out of sync with who ever is speaking, then it goes quiet agaqin for another couple of seconds then its alright and back to normal for a while!!

Did this on quite a few occasions but mainly seems to happen when watching programmes that i have recorded on Sky+!!!!

Really starting to piss me off now