You might try checking whether you have all of the latest updates from Software Update. I just received a new Motorola RAZR V3 from AT&T and it syncs with my MacBook Pro via Bluetooth and USB without any connectivity problems.
Note: if you register your phone using Bluetooth, you'll need to deregister it first before using a USB connection, and vice versa.
Here's what worked for me:
1. Turn on Bluetooth on my Macbook
2. Turn on Bluetooth on my RAZR V3
3. Make the RAZR discoverable ("Find Me" -- which works for 60 seconds only)
4. Start the Mac's Bluetooth Assistant, tell it to find your mobile phone
5. Once it's found, walk through the prompts to pair the phone with your Mac
6. Start iSync, set your synchronization preferences, and sync away
Note: I haven't been able to sync addresses, notes, or custom Address Book fields from my Mac to my phone, but all calendars seem to sync without any problems.
Good luck!
Regards,
Steven