Make 100% sure you have entered the correct wireless password/key.
9 out of 10 time i come accross this sort of problem it's down to incorrect password.
Just to add, if you want to check if its a password/key problem, try turning wireless security "off" in the router settings. Then see if you can connect. Obviously then turn security "on" and re try the password.
Edited by deleted (Wed 12-Aug-09 08:18:47)