Have you had the phone flashed to V4? Read the sticky's in this section mate, there's plenty info in them and i'm quite sure this has been covered?
From another thread
*#0000# displays the firmware version, under 4 you wont be able to use TomTom 6 on the N80... You can upgrade the firmware on your phone using the USB datacable that normally comes with the phone, go to http://www.nokia.co.uk/A4226014 download the software from the Nokia site, connect your phone and it should download the latest firmware for you