Accounting Module does not recognize shared secret

Hi I just found out that im getting error in accounting module. It say that shared secret is incorrect, but it was working fine for more then a week. Also im using DNS name in the NAS Name filed instead of ip address. Why am I getting this error? Here is the error message? rad_recv: Accounting-Request packet from host 192.168.0.10:61296, id=39, length=143 Received Accounting-Request packet from 192.168.0.10 with invalid signature! (Shared secret is incorrect.)