An incomplete activation could very wel be the problem. Sometimes activations don't complete. I've been told by our BES admin that corruptions in contact lists or other databases can cause it. Also, it's a good idea to clean out all the phone call logs on the device before replacing/upgrading it. This deletes the phone logs on the server thus speeding up the activation. When activations hang I have had good success in the past by cancelling the activation and having the BES admins setup an OTA password and activating again. It's always gone through for me on the second attempt.

Hope this was helpful.