Hi Toni.
Nobody's answered this in the last couple of days, so I'll tell you what I can.
This error is generic in nature and the few times I've seen it, it has related to a misconfiguration on the ACS (different types) with different wireless authentication methods (EAP-FAST, LEAP, etc.). To really track this issue down though is going to take some debugging with verbose logging, and that wouldn't be prudent to put on the forum (due to the sensitive nature of some of the logged messages), so I think the best thing I can do is to recommend you open a TAC case on this so that in-depth debugging can be performed.
Sorry I can't do better than that.
-Joe