Hi All, I have identified the source of the inbound authentication, and what appears to be outbound authentication. The server was previously "alive" with the same server name and role, however had faulty hardware (can you say cheap and nasty SATA-RAID). After the conflict was resolved, the server was rebuild using the same machine name. W2k3 SP1 was installed, ISA was installed and everything went downhill from there. Removing the computer from the domain, applying a new sid (sysinternals NEWSID program) and then rejoining the domain has resolved (or appears to) the issue. Thank you VERY much Tom for your assistance and everyone else that assisted with this issue! Anthony.