Be sure to change your APN to epc.tmobile.com also. The *.voicestream.com APNs are being phased out. I'm using my 8320 with the TomTom with no problem.
Also, I think you need to change the dial string to #99*. I ca't remember if it defaults to that or not.
Also, I think you need to change the dial string to #99*. I ca't remember if it defaults to that or not.