I just picked up an AVR630 a couple of months ago and it is connected to a cheapo JVC xx44SL prog scan DVD player. Sometimes (about 20% of the time), I put in a disc, it will say Dolby Digital but only the L/R speakers are working. I turn off both units and turn on again and it will get fix and all speakers indicator will light up. What is the culprit? DVD player, amp or faulty optical cable? (Monster brand). I doubt it is the disc since I have put on a couple of brand new discs and it happened. Thanks.