David,

I don't know if PDANet is WM6 compatible, and odds are that it is interfering with the DUN hack. You should uninstall it and reinstall the DUN hack. Also be sure to remove all partnerships from both devices. Also, you might need to manually apply the hack from the XDA-Dev thread.

Reset the phone and re-pair after all of that. Check the Cingular settings, give it a try and let us know.

Ninja