Glad we're making some progress, Dave. Let's see if we can get you sorted out properly.
I know for a fact that WGT runs really well on a Mac... My associate has a Mac and he rarely has any connection issues and hardly ever suffers the meter stutter, so it is possible to play.
Having said that there was a point about 4 or 5 months ago that he was experiencing the time-out errors like you have described. Not being a Mac-guy I can't tell you exactly what he did to correct it, but it had something to do with 'resetting permissions'. Maybe someone who knows more about Macs can expand on that.
Also, I would suggest "game booster". Cuts off all unnecessary programs while you're gaming. (Hope it works on the iMac... lol)
Good luck.