No more connections can be made…

i have a win2k server running as a dc with dhcp,dns,wins,iis on a 8 pc network which i also use with other pc’s in for repair.
i have 20 licenses on a per-server setup.
it is now telling me that i cannot connect to the domain: “No more connections can be made because there are already as many connections as the computer can accept”.
1. what is wrong?
2. how can i fix it?