Actually, come to think of it, my N800 with the latest OS has been acting funny as well, only since I upgraded it. The volume level when I was jogging just now went from low to high without my intervention. I had the screen and all turned off via the hardware menu.
This happened several times, not just once. This has NEVER happened to me, in the other hundred or so times I've been jogging with it. The other weird thing that happened BEFORE I went jogging is that when I ran YouAmp, the sound came through the speakers EVEN THOUGH I HAD HEADPHONES PLUGGED IN. I couldn't fix that, but changing to another media player (MediaBox, I think it was) got rid of that problem, but later is when I had the volume-changing problem.

I'm using that app "powerlaunch", for what it's worth.