Reset your 8320. I had to do this also ... from what T-Mobile said, some devices have incorrect security and this clears it up. I didn't believe it until the tech, who I started to trust, told me this. He confirmed with the onsite BB rep.

Backup the unit first. Afterwards, go to the security options, general, menu - wipe handheld.

After a reboot, it will sync the service profiles and then if you are a BES user, it automatically re-registers and starts to sync. That are the steps I remember

Good luck.