I had the same problem some time ago. What I did was while charging I connected my N800 to my PC with the usb cable, turned the tablet on while holding the swap key, had the Software Update Wizard running on my PC and the latest Diablo image on my hard drive of course. Then as soon as the USB icon appeared on the screen I flashed it. Simple as that.

The thing is you have to be really quick about it, I mean using the wizard, otherwise the tablet will reboot again.

Hope that helps.