Thank you for all your responses.
With all your help we have narrowed it down to a software bug and a customer
running a port scan. We were running Version 12.1(3a)T2 IOS and one of our
customers decided to run a port scan (We called them and asked what was he
doing). Someone told us to look for '%RCMD-4-RSHPORTATTEMPT:', we did and
found it just a few seconds before the router rebooted. He referenced that
attempt with the IOS a determined it was Cisco bug CSCds07326. We have
since upgraded our routers to the current IOS. Again thanks for all your
help.
Shawn.