The PC and the Mac is on the same network with the same router end, so there's no difference there. Also when it didn't work on the Mac it worked fine on the PC, so I doubt it's a server issue either. Also the behavior is ALWAYS the same on the Mac, there are no differences in lag, wait etc. I don't think the hardware is the limit either, not even on the macbook pro 13, it's something else about the connectivity to the SL servers.