"Connection Timeout" with WPA2 wireless Macbook 10.5.8

I had to set our Airport Extrreme (g) network up with WPA2, so that it could work with our HP wireless printer and other technologies. However, my Macbook will not now connect to the Airport network, after all machines initially working fine. Even though all other machines on the Airport network connect fine, via 10.4.1 and 10.5.8, my Macbook only now connects via ethernet. I see that other people seem to have had similar problems and am intrigued if there is a way round this for my set up? I have admin access but can not go as far as to reboot the OS system since it is a work laptop. My Airport connection worked stably on WEP by only for a very short time on my home network. My work have since reloaded the system but it has made no difference and I still can not connect to my WPA2 Airport connection from this machine, which is amazing!