Have you very good reason to upgrade the firmware ? So many users has reported WBPN bricked beyond repair after upgrade.
Cisco has never responded those threads, but I suspect there are at least two WBPN hardware revisions. First one is supported by 1.0.1 firmware while second one by 1.0.2. Old 1.0.1 has allowed upgrade to 1.0.2 causing bricked WBPN, recent 1.0.1k may be updated not to allow upgrade to unsupported firmware.
Just guessing ...
I would like to recommend you to consult upgrade with official SMB support center.