Hey Rick,
I'm having a somewhat similar problem. My computer says it is connected to the internet, but it is not really (same happens to a wire or wireless connection). I checked the firewall is not attacking the wireless by turning it off... and I still cannot connect to the internet. Also, I've tried some stuff on cmd but they don't work either.
I've tried what you suggested, but on the advance tab I get no antenna diversity option. The only one that gives me something with AUTO as an option is a "IBSS 54g(tm) protection mode"... but this one has only two option: AUTO and DISABLED.
Thanks!!