FreeRADIUS Proxy Problem

Hi all, I've got a really frustrating problem with FreeRADIUS trying to proxy to a Microsoft IAS. I'm using FR 1.0.1 (I know, it's old). The problem is that I have proxying configured, but I keep getting Access-Reject back from the IAS. The IAS says that I used an unknown username or password, but I know that the username and password is correct. I know this because I have a test FR box with the same config and same version (1.0.1) that works fine. I assume that the User-Password is not being passed on properly, but I can't imagine why. I looked into the PAP authentication config and both the working test box and the non-working production box are configured to use 'crypt'. Can anyone point me in the right direction? Thanks, evt