I know this is an old thread, but I recently experienced the same problem. I’m running 2.0.RC1.
Examining the CRL showed that it had recently been renewed around the time that it started to be reported as expired. Somehow the renewal of the CRL did not get communicated to the running instance of the RADIUS server.
I found the simplest workaround is to disable and then enable the RADIUS service, which I guess caused the renewed CRL to be read.