Every now and then I have a problem like that with my router after reformatting a laptop. I use a higher version of security than most folks on my router. Strange as it sounds if I can't connect I have had some success turning off security so it's an open connection. Then the computer connects successfully. Then I turn on security, Windows complains and I stick in the password. Then it can connect.
Not sure why this worked. I'm also not sure if you even use a password on your router.
i have a laptop that is brand new sony and it has wifi. i also have a linksys router. My laptop is able to connect to any network i try except my own. The router can successfully send wireless signals as my ps3 and wii can pick it up. but Again as i try to connect using the two it doesnt work. I had success with that setup only when the connection is wired through ethernet. generally vista wil say unable to connect