I've had no problems with Linux, but for some reason the Windows bluetooth connection doesn't work as easily.

With the standard XP bluetooth setup, the connection always stalls at the end.

For N900 you need to have the bluetooth dial-up networking (DUN) installed. For XP (probably same with Vista & Win7 ?) you need to install the Nokia PC suite. Connecting N900 with the suite creates a new dial-up connection using Nokia drivers that work for me.

You don't actually need to use the PC suite once the Nokia dial up option has been created under network connections.