I totally agree with the battery comment. If you can swap out the battery with a new/borrowed/fully charged and then use the Flasher program to reflash, you should hopefully be okay.

I know this from unfortunate experience; my phone was down for most of this last week - I live in a town of over 150,000 and there were no N900 batteries to be found anywhere. (I ordered my N900 online.)

I ended up buying a generic camera/pda battery charger at an office supply store to give it enough juice to enable flashing so the phone would quit rebooting every 15 seconds. I know that I won't ever try to do a major update like 1.2 again without an extra battery on hand.

The OTA update should check the battery status as well as free space, IMO. (If it does, I don't recall seeing it.)

Terry