I have a EVO 4G and i had some weird BT connection issues as well. However it was only after upgrading to Sprint's Version of Gingerbread. I here are the problems I had and what i had to do to fix them.
1) Phone would connect but couldn't transfer Contact or sync PhoneBook. After pairing my EVO would pop up a message asking that the "Pioneer unit is asking to sync phonebook" I would click 'Always Allow' and nothing would happen. To fix this I had to delete the bluetooth pairing on the Z120. To do this i had to "reset to factory defaults. I also deleted the pairing on my phone. The