3G service has been in an out for the better part of a month. Doesn't affect everyone and seems to affect different people at different times. An ESN swap is where the tech deactivates your phone by activating a dummy ESN (Electronic serial number) for a few minutes, then reactivates your phones ESN. It's worked for everyone who has done it. You have to call vzw tech support, tell them you have no 3G service, you've tried the *228 activation and the factory reset (even though you haven't, but if you tell them you haven't they will tell you to do that and it's useless), and they will do an ESN swap for you. If the ESN swap doesn't fix your 3G, you will need to talk to a tier 2 tech support and have them do a DMU reset.
Oh, and ODIN may not work on a mac, but Heimdall should.