i am unable to telnet although it was working before

I M NOT SURE WHEATHER ITS APROBLEM AT MY END OR IT IS AT UR END..BUT IWAS ABLE TO USE THE LAB ONLY ONCE AFTER THATWHENEVER I M TRYING TO TELNET AS PER SCHDULE ITS SHOWING ME THE MESSAGE THAT "WE ARE FACING THE PROBLEM OF FIREWALLS,PLZ CONTACT ADMINISITRATOR".AND I AM SURE THAT THERE IS NO FIREWAL ON MY COMPUTER,BCOZ IWAS ABLE TOUSE TRHE SAME LAB BEFORE............PLZZZZZZZZ.........HELP