If you open browser or maps, does it work?
No, no incomming traffic appears on bytes received, on send are a lot.
Do you have a media player connection between your phone and the car?
The DUN connection cannot be used for automatic sync as it seems. So you need to manually refresh emails, etc.
I cant use any online gps map either...
It is connecting from time to time, doesnt follow any rule or trigger. Also i left the GPRS APN to empty. Nothing works