Problem with pam_radius_auth

Hi, I'm testing Freeradius in order to autenticate squid user trough PAM module. My architecture is: SQUID SERVER --> PAM_AUTH_RADIUS --> FREERADIUS --> SQL DB All work fine but frequently in /var/log/messages I see this message: Safesquid: pam_radius_auth: radius server 212.80.192.120 failed to response Safesquid: pam_radius_auth: All radius servers failed to response What can I check to solve this problem? Thank's, Maury76