The router is a Cisco, I do not have access to this puppy, but suspect it has some sort of loopback feature set.
Reboot --- ok, I'll add a script to /etc/rc.d/init.d/ to plug in the arp entry I need on reboot.
While this is a good work around -- I'm really interested to know what is causing it.
I'm going to capture the bad mac address and then get the router folks to see if they can identify what ip address its associated to and from that see if we can isolate the culpret machine and configuration.
thank you for your input -- I appreciate it.