Since Windows server only gives you 2 remote connections, it’s easy to end up “locked out” of the server.  To overcome that, you can actually use a third remote connection that allows you to get in and kill the other offending connections.

On Linux type:

rdesktop -0 1.2.3.4

where 1.2.3.4 is the ip address of the server that you want to connect to.  Obviously, you need to have rdesktop installed and it should be a fairly recent version.