Maybe the power socket is faulty.
My n800 fell (a long time ago), it almost broke the plug (it was bent) and the socket.
I had to push a tiny amount of foam in the socket, behind the negative plate, so that it made good contact with the almost broken plug.
It worked for many months, then the plug broke completely, so I replaced it with a cheap ca-100 (usb charger) knock off from dealextreme.
It worked for 2 weeks, then it stopped working.
I simply pushed a couple of strands of fine electrical wire inside the plug. It's been working well since last august (from time to time I have to put another couple of strands of wire).
I don't know if the cause of the problem is the cheap plug or the half broken socket, but I don't really care as long as it works.
You could try it as well, just be careful not to short the contacts of the plug (the strands have to stay completely inside the hole of the plug, so they shoul be 5-7mm long).