unable to set telnet state

I set up a peer to peer network 1 month ago, I was able to telnet to a unix server on the network. Then i lost the connection, the user claims nothing has changed,( of course!) however I can see the network and I can ping the server IP address I cannot however telnet through windows or through procomm plus software, both tell me unable to set communication state telnet. I have used a laptop from the same network connection and it works perfectly. I know my protocols are correct however, becauseof network connectivity, what else might stop it