Using N800 & 2008 OS & Apple Wireless Keyboard!
Get to the dialog box where the n800 identifies the Apple KB and generates a passcode.
THEN

TYPE THE GENERATED PASS CODE ON THE APPLE KB & HIT RETURN ON THE APPLE KB

Click ok in the n 800 dialog box and if all goes well they should be paired.
I have had better results using the Nokia KB setting rather than the Generic

If you need accents etc hold the option key down and press all the other keys and you should have your fill :-)

Great keyboard

Hope this helps