When trying to connect to the internet from my laptop, using phone's bluetooth modem, I encountered error message like: "Failed to connect to the network! The modem may be used by another application or the modem may not be configured properly."
I solved the problem by following the procedure found from http://discussions.europe.nokia.com/t5/PC-and-Mac-Software/One-touch-access-Bluetooth-Modem-error/m-p/144134#M18310