OK, I do realize this thread is like 100 years old, but I am having a weird, yet similar problem. Unlike the above, mine does not sit unused and gets regular usage ant a normally loud type of movie volume and I've never had any issues. I have been having problems with the neighbors playing their music loud in the middle of the night and have asked them to keep it down. I built my home theater in the basement to specifically minimize neighbor issues, but did have the previous neighbor in the house in question tell me jokingly that the dishes in her cupboards were rattling.
Anyway, to get to the point, I decided to give them a little sample of their own medicine and pulled out the DVD Audio version of the metallica "black" album at 3 AM, diled the 15" sub up another notch and let it snap around 3AM with no problems. My message was received loud and clear. Nothing strange happened during that approximately 10 minutes, and I was way under even being close to any limits. I shut it down and went to bed. The next night I went to watch a movie and had kind of a staticky buzz that was annoying, which I blamed on my PC being overloaded with background activity, so I shut down the browser and it went away and everything was fine. None of my speakers or anything have any issues and the sound was crystal clear as usual.
The problem is that this issue keeps coming back, and it seems to last until I run enough content through to "warm it up" and then just like the first time everything goes back to normal. I have tried turning it on 10 minutes before I run a movie to warm it up, but apparently that's not enough load to do much. Mute has no effect. I'm using the 7.1 inputs so it normally stays on Bypass the whole time - everything runs thru the Oppo except a bluetooth thingy I have on there. I realize I might have messed something up, but why does it go away after about 5 or 10 minutes of movie? Nothing has affected any connections, and I have so much connected to it that it would be difficult to just pull it out and go snooping around. Any Ideas. Not sure I can afford to send it in right now - job situation thing. Every single speaker except the sub has the same crackling sounds - it's not just one channel.