That most often comes fromthe fact that network drives are 'mounted' with ports in that port range on windows.
Afaik, only a reboot can cure this.
On windows 2000 the command "netstat" will tell you which ports are in use at any one time. Try netstat -a-o, which should give you a list of all open ports and the PIDs for the processes that are using them. You should be able to find out what is grabbing the port. In my experience, its usually something like a firewall client, or an IDE that has not shut the server down completely.