wireless connectivity problem

I just installed a new router: Netgear N900 which works perfectly on 3 computers but fails to connect to a fourth which is further away in another building. This desktop computer sees the network, has 2 bars but when the box comes up to put the network key/password in, fails to connect. The computer is an XP which is compatible with the new router and also connected with the old router using the same security encryption (WPA-2). What can I do? Thanks for any help offered!

there are some known issue between windows xp and wpa2. update your os would fix the problem.