Whenever I try to join a game using version 2.5.1 on Vista, it just lags terribly and shows a little clock graphic in the corner.

I have comcast high-speed internet, and my connection is usually pretty good, but not working here.

Anyone know the problem?

1. Do you have wifi?
2. Is the router Linksys?
3. Does the model number contain "WMP54*" where the star is other numbers?
If you answered yes to all of the above, then you are experiencing bad packet loss courtesy of Linksys's underpowered router.
That's the only help I can give as I had that problem myself.