Sometime last night (or more accurately in the early hours of the morning) my Server 2003 box decided it wasn't going to have a default gateway anymore. The problem first made itself known when we started getting "Mail Delayed" messages back from Exchange. On investigating the problem using Remote Desktop I found that even though a default gateway was set in the LAN properties, "ipconfig /all" and "route print" showed that the box wasn't honouring it. I then made the brilliant decision to disable and re-enable the LAN card.
D'OH! Remember, I was using Remote Desktop to do this! Luckily I had an EMS connection to the Server so I was able to re-enable the connection from there. I'm lucky that 2003 supports this, unlike 2000, else I would have to crawl around attaching cables to my headless server.
(Image lost due to Blog move)