can't connect ipad to wifi

we constantly have issues with customers bringing in Ipads and other apple devices but have difficulty connecting to our nortel wireless antennas. Our wireless antennas broadcast in a/b/g. Not all apple devices can't connect, infact we have 10 ipad2 inhouse that all connnect, but various other clients will occassionaly have success and often times can not connect. Seems to only be apple devices that give us this problem.

We have tried unsecure networks, wep , wpa and web authentication, but the problem seems to persist. Not sure if this has anything to do with it, but our gateway has a home page redirect. Do apple devices see this as a security risk and refuse connection?