Thanks DJames1 - it was the power adapter.

Not having a voltmeter handy, I took it to Radio Shack. A sales associate tried an igo a69 adapter and I was pleasantly surprised to see the "Charging" message pop up immediately (I really though the n800 was at fault based on how quickly it went from a tad flaky to outright failure). I grabbed an adapter along with the a69 tip and I have a fully charged n800 again.

I'll see what I can do with the wire some other time - I won't mind having two power adapters.

Thanks again!