I just wanted to add to this thread my experience. I took delivery of my Volt in December of last year. I paired my EVO 4G from Sprint at that time and had ZERO issues with bluetooth. It worked perfectly for 5 1/2 months or so. It was running Android 2.2.
A couple of weeks ago, Sprint sent out an OTA update that brought the handset up to Android 2.3 (Gingerbread). Ever since then I have the problem described above, phone connects, then disconnects, then reconnects. It is completely unusable. I've had the same phone, and the same car. The only thing that has changed is Android 2.2 -> 2.3. Now, that update also included a "Radio Firmware Upgrade", that is independent of the OS. So it could be that firmware upgrade or the Android update I suppose.
I'm going to try the "deny phonebook" hack as well as try rooting my phone (when an exploit is discovered) and try a different OS variant and report back my findings.
Silver Ice Metallic Volt #210
Delivered December 18th in Orange County, CA