Just spoke to RIM support. The 8320 has a known issue on switching from UMA to GSM when bluetooth is in operation. It simply disconnects the call. I spent over 3 hours trying to figure this out with several tech support reps. I finally figured it out on my own and then called BlackBerry. Was finally transferred up to RIM level support who said they are working on a fix.
8320 UMA/GSM switch over
