Router has a good signal, but laptops aren't recognizing or connecting well. Other items have no problem?

Ok, so out of no where I'm having connection issues. I've got a Belkin-G router, but can't get into its settings because I forgot what a friend of mine renamed it. (ex. it's no longer 192.168.1). Anyway, my macbook won't connect at all. PC laptop will connect, but I am continually having to run diagnostics to maintain the connection. However, the XBOX 360 which is hard connected is connecting fine. Tivo which has a wireless connection is connection is connecting perfectly. Any ideas on how to go about fixing this? Ran diagnostic on macbook and it's asking for a pword for the router. Router is not pword protected.