HELP Problem using BB as tethered modem for Macbook pro

Hi Ive googled the tutorials and such but cannot complete the last step on connection. Its a BB Bold 9700 (using South African network MTN) with Macbook pro. Im using the USB cable, Mac picks up the modem under system prefences, network. Account name and password is left blank,Telephone number is *99# or *98# for MTN network and APN is internet for that network which I have confirmed. Vendor is RIM and GPRS option is on rather than CDMA as GPRS is used in SA. When you try connect is gives error cannot connect to PPP or something along those lines. Spoken to many technical guys they all say everything is correct and cant figure out why it wont connect.
Is it a problem with the BB sim perhaps or settings on that side? Or does the Macbook sit with the problem?
*Note one friend was able to connect a BB to macbook pro as modem in similar fashion so it is possible just got this hurdle to over come..

Any help will be gladly appreciated