Samba
I booted up my machine and had a problem connecting to my mapped drives on my Linux box. It just plain wouldn't see them, wouldn't even see the computer. So I rebooted thinking Win2k must be a little screwy. Same thing. So I get into my linux box and realize that Samba isn't running. I start it and it never loads. Check the logs and it's giving me an error about my hostname. I had just recently changed it. As soon as I put it in /etc/hosts it starts up and works just fine. Weird.