Tether

HI i am new user to use this amazing software, i got Blackberry 9000 bold ,phone come from AT@T USA and i am using it here in SouthAfrica with Vodacom simcard,sim is activated for BIS.
when i try to connect it in Blackberry via USB so always got 2 error.

(The application tether has attempted to open a connection to a location inside the firewall and outside the firewall which is not allowed by your IT policy)

(Failed to find an available port.please exit the application via the manu and try again)

I am very interested to use my BB internet with my computer, i will buy this software if it will work.
Regards