I suppose the cause is a failing spindle motor...Before you do that, I'd recommend calling Sony...I had the same problem happen with my DVD player yesterday...
Even if you physically turn one off, sending PLAY to the other one will turn the first one back on...If the Off command works, then a macro for Off|Power Toggle will always be On...I tried all the CCF files, MXF files, and tried converting the Sony universal Group 1 and Group 3 IR codes into CCF and nothing works...
But then again...that's why they make fullscreen versions of movies...By July, it was unable to read any DVD...I Burn tv shows onto DVD with my Sony laptop,and listen to some mp3's too...
I've had this CD/DVD player for about 2 years and I like it except for one annoying problem...I've decided to keep the new player even though the NS425P works as it should now...