I am trying to add an Airport Express as a client into a wireless system anchored by an AR423W by Airlin101 wireless router. The Airport Express will hook to my stereo. The Apple Airport cannot find network and the Airport Utility software will not find the Apple Airport Express. I am running WAP2 AES encrypted security on the router. Any ideas what causes the problem?
Start by turning off all wireless security until the connection works. Personally I find Apple's terminology regarding security protocols confusing so I can only suggest trying all available options until one works with all your gear.