Uncommunicative server

I recently set up a server to handle my home network. It is running Server 2003, without any service packs (I think). I connect it to my other computers through a switch. At the time, only one of my computers can be on a domain-based network, an old computer running Windows 2000. Everything was running fine, I had set up multiple users which sychronized after each log out, and stored data on the server.

The problem started when my mother unplugged the server. While it was still on. When I started it up, it said that a certain .tmp file couldn't be synchronized. It said that about a dozen times, then booted. My client computer had a similar error involving the same file. Now, no matter what I try, they won't communicate. Anyone know why?