EAP-TLS constant disconnects

Hi all! We've been using freeradius 2.1.12 with EAP-TLS authentication. The problem we experience is constant disconnects of the clients. After an some time (it seems like the intervals are random) of usage the connection drops. I don't have a debug output, since the server is in production allready and because of the valid traffic it's hard to efficiently debug it that way. A similar problem was allready reported some years ago (without an answer - at least not in that thread): http://bit.ly/10o9xkG Any ideas (what may the cause be, how to debug it efficiently etc.) are welcome! Regards!