wpa security is missing all of a sudden.

I have had 3 calls today from customers with win xp, showing either sp2 or sp3.They cannot connect wirelessly with the wireless zero client. The connection does not make.Two were trying to connect with wpa, and when we tried to manually configure, the wpa option was not there. Since the network had not changed, I believe the wpa was previously working.The third user was trying to connect with wep, and it kept trying to add the aes encryption to the connection.Any help you can give?