Had no problems using my Nokia 6630 and now a N95 with both G3 BlueTeeth and SUB interfaces on MTN, but absolutely no joy with my Vodacom SIM card. On my MacBook Pro, the network connection would show, "connecting.....authenticating...disconnecting ".
Read, 3G Bluetooth and USB, unless your name is George...
I dug around a little further into Ross Barkman's scripts 3G CID1 and 3G CID2. Turns out the one to use is 3G CID1, but in the profile, in the space for telephone number, put, "internet" (without the quote marks). No account name and no password. Read the .rtf that comes with the script zip file, which explains how they work.
The Vodacom support staff have heard of Macs, but really battle. They keep telling you to play with modem setup strings such as "*99***1#". These are explicitly not needed with Barkman's scripts.
Hope this helps.