Ok, for those of you who have a Plantronics Voyager Pro bluetooth headset, I got a connection/"pairing". This is what I did:
1) I turned off my bluetooth headset.
2) Go to Settings in iPhone and turn "on" your bluetooth so that it is searching ...
3) Then I turned on the headset until I saw the blue light, AND CONTINUED to HOLD DOWN the on/off switch until the blue light was FLASHING.
4) The "pairing" took place during the flashing.
Holding down the power button on your Voyager Pro headeset acts like as a "hard reset", and starts a "new" search for a new device or new software, in this case it's iOS5 or your new iPhone, or both.
Before doing the steps above my iMac (desktop computer) had the same problem of not "discovering" my bluetooth headset. But after I did the steps, I set my iMac to "discover mode" and the "pairing" between these two devices was successful.
OTHER bluetooth headsets
Try doing a "hard reset" on your bluetooth device, if you are trying to connect with an iPhone, iPad, or desktop computer that is running iOS5 or Lion.
The problem seemed that my bluetooth headset was trying to connect with devices that were paired with previous operating systems (ie: iOS4 or Snow Leopard). When I upgraded my operating systems to iOS5 and Lion, my bluetooth needed to "start fresh", hence the "hard reset" on the bluetooth.