Hi Lee
I don't know Cisco 2106 WLAN controller very much but I have successfully got FreeRadius to work with AS 5508 Wireless Control. It's a EAP-TLS configuration with openssl selfsigned certificates.
AS 5508 Wireless Control and several Cisco Access Point Software Version 6.0.196.0
FreeRADIUS Version 2.1.8
OpenSSL 1.0.0-fips-beta4 10 Nov 2009
Which is your configuration? More information you provide easier solve your problem.....
Run radiusd -X in a terminal is very important..
I hope it helps
Regards.