Thanks a lot !! I just got an Optus wireless HSDPA modem for my MB Pro. The sales staff assured me it worked with Macs out of the box. When I got it, ran the Huawei Mobile Connect App that comes with it, it failed to connect. Hours of waiting on the phone for Optus Tech support was a waste of time. When I finally got them, all he could say was re-install and reboot - typical windows mindset. He even got a bit testy saying I was wasting his time!! But your instructions worked like a charm. I am connected at the highest speed the modem is capable of.
One note: One of the comments above mentioned entering something in the PIN field. The Optus modem came without a PIN, and it is working fine for me with the PIN field blank.