[Serusers] Cisco Phone question

I've noticed that with SIP v6.3 on a Cisco 7960 the phone periodically has registration problems. A show status at the phone interface shows the message "E630 REG retries exceeded". If I try to force an un-register then re-registration sometimes it works and sometimes I get "E630 REG retries exceeded". I've looked at various timer values but worst case is that I am using the defaults. For any timer that was changed the change was in a positive direction. Cisco does report registration problems in version 6.1 code but they are suppose to be fixed in version 6.3. Has anyone else seen this behavior? If so do you have any suggestions for what might be causing it? Thanks,Steve -- ISC Network Engineering The University of Pennsylvania 3401 Walnut Street, Suite 221A Philadelphia, PA 19104 voice: 215-573-8396 215-746-7903 fax: 215-898-9348 sip:blairs@upenn.edu