MacBook Pro will not join my router - please help

Hi,
My MacBook has been functioning fine until I installed some necessary updates last night, after which point my laptop no longer will join with my wireless router. I see my router, but when I try to click on it to join it doesn't do anything except 'think' for a while and then...nothing.

I know it's not the wireless router, my iBook and Toshiba connect fine - but it's just this computer. I took it to the apple store and they had issues at first, but then got it to connect to their internal router. I'm not sure what to do, if it's a settings issue or what. I'd appreciate any help, this is frustrating! Thanks!

Vanessa