MIC Failure

Anybody know what the following means:

disconnected, got deauth: MIC Failure (14).

The AP is a MT 112 w/SR2. CPE is a Tranzeo CPE-90.

Thanks

http://wiki.mikrotik.com/wiki/Wireless_Debug_Logs

The MIC failures are coming from a customer’s CPE. Which I verified it has the proper key.

Any ideas why it’s doing it.