I am losing connectivity to my primary domain controller intermittently. I have access to my secondary domain controller, all other servers and pc's. ThePDC is running server 2003 enterprise sp1...all other windows xp sp2 clientsconnect and work fine with it. I installed another vista machine and get the exact same results. Both machines are using completely different harware. I have run the arp utility on a hunch that the table isn't refreshing properly and found that the Vista systems are mapping the physical address for our firewall to the DC in question.On occassion it gets the right physical address, and connectivity functions as normal.