I had this message recently. The first issue I found was that the username entered into the laptop was not correct (I had djohnson, need to have DJohnson)
The second issue I had was that my AP's were not authenticating to my WDS access point. I had turned off LEAP on my ACS server by accident causing the WDS authentication to fail. Once I turned this back on, my AP's authenticated to my WDS device and my users authenticated to the AP's.
Otherwise, the meaning of this is that the certs are not matching up correctly with the server either due to expiered certs, incorrect cert type on the users machine or incorrect information in the cert.
Hope this helps.
