Here is a quote from TomTom support regarding upgrading from TomTom3 to TomTom5
With navigator 3 gps driver versions 2.08 and higher the commport was locked to prevent conflicts from third party applications.As a downside it prevented other applications accessing the port.
Navigator 5 GPS does not do this.
If you have upgraded to Navigator 5 from Navigator 3 there may well be remnants of the old GPS drivers still blocking the port.
We would suggest removing all Tomtom from the PDA
Start/settings/system/remove programs and then make a fresh installation of the Navigator 5 application from the upgrade CD.
You should then be able to use third party applications with your GPS.
With best regards,
The TomTom Customer Support Team