Have you tried resetting the SU-8W, by pressing and holding the two blue keys at the right side (envelope and sync icons) for about 30 seconds until the leds at the top start to alternate (looks completely different from the regular short blinks you see when it's powered on or accepting a connection).

As you've previously paired the keyboard to the N800, the keyboard still remembers the N800's Bluetooth address and key but the N800 doesn't remember the keyboard after the reinstall, and this could cause some problems.