File Server Problem

I have attented an interview and I was asked the following question. I would like to know the exact answer. Pls help me.

Q) 1.There is one win 2003 acting as a DC, DHCP and DNS.
2.have a one member server which is a file server and 100 XP Pro. All computer receiving IP from DHCP.
After restart the file server, one of the users can’t connect to file server.

A error message (BATS NOT FOUND)is appeared in Client computer.

PLEASE HELP ME.

regards
Arun