TomTom's GPS driver constantly holds open a connection to the Bluetooth stack on the Pocket PC which results in a failure with any other application wanting to talk to a Bluetooth GPS.
To correct this, please follow these instructions:
On the PDA...
1. Go to START | SETTINGS | REMOVE PROGRAMS.
2. You should see a program called TomTom ~ GPS
3. Tap REMOVE and answer YES.
4. The new TomTom Wizard will appear asking you to reset the Pocket PC, tap the OK button.
Now, you will have a fixed connection and you will be able to use other applications again with your Bluetooth GPS Receiver and not be confined to just TomTom Navigator.