I have not tested this, but, I would think you could use this to upgrade to ZB21 if the upgrade failed to do it. The radio only effects the phone, not WIFI or BT. Not sure if there are any other benefits/changes to the ZB21 radio. I have been using YH25 with WM5 from the beginning and have had no problems.

John_k,

Yeah using the YH25 phone image will restore the tethering capibility. I am not sure if vzw was intentionaly trying to block it, or it was a bug but ZB21's radio does not tether without additional software.

,Dave