Usually when you cant get out, you havent fully associated to the AP. You might have the wep key right which gets you into the radio, but if the rest of the authentication is wrong, you will not get an ip address. I found this out doing LEAP, I associated, the AP showed me associatied, but I could not get an IP address, my password was wrong, but the WEP key was right. You might want to run a debug to see if your MAC authentication is the problem. Disable MAC authentication and see what happens.