Problems connecting to WiFi
I had a similar problem.

In my case when I pulled down the airport icon it saw the connection, but would then not connect. Along the way to not connecting it would ask me to enter my password. Even after entering the proper password it would not connect.

I finally solved the problem by going in to /Application/Utilities/Keychain Access.app and deleting my home wifi's stored password.

The next time I connected - it asked for the password and from that point on it has connected just fine.