I fixed my non boot problem - took the n800 back and exchanged it.
Maybe I've become overly sensitive but I seem to see a problem with the new unit.
The four-way and back/menu/home buttons on my replacement seem to be broken - in that they wobble too much when moved.

Hmm, hard to describe. If I put my thumb on the raised portion of the 4-way and wiggle it the 4-way and the back/menu/home buttons both have a lot of freedom of motion. They move together like a couple of loose teeth.
I don't recall this on my previous N800.

It's almost as if they are captive - but not attached to anything. Although they seem to function as they should. Has anybody else experienced this?

same on mine. the only 'cheap' part of the n800 that I notice!