It's kind of funny, my N800 (bought in January 2007) also started to behave strangely the last few days. It was off in the morning, something that hasn't happened since I fixed it to never start the crawler (half a year ago). Put it on the charger, everything looked ok. Then it happened again.

I then started to keep an eye on it, yesterday I charged it at work (it was off in the morning _again_), wondering if the battery had finally conked out. It was fully charged when I left work, but at home it had turned itself off. Instead of putting it on the charger I just booted, and the battery was just fine - no discharge. I kept it connected to my phone all night and checked that everything was fine, no CPU use, email etc. working OK.

This morning it was still OK, battery fully charged. This afternoon I checked it again, everything OK, then drove to work. It was off again when I came in to my office. I've checked the battery, it sits snugly, so it shouldn't be caused by a spurious power break, but at this point I don't know what could cause it. When up and running everything is looking just as it always did - no problems.