I need to check this out. I had the random connection problem with my 90bt and 3g iphone that drove me crazy. I bought the Apple cable, have all the latest firmware, etc.
Then a couple weeks ago, I had my iphone replaced under warranty for a screen problem. I did a restore through itunes, and all of a sudden I couldn't get it to disconnect from the 90bt no matter what! I was so happy. It lasted a week and a half, and then started getting random again. Not as bad as before, but getting close.
If we could figure out what itunes is doing to screw it up, then maybe we could deal with it.