Ask your IT/IS people. They could have started blocking IRC due to abuse (people sending and downloading files or whatever). Colleges/Universities change their policies on what they allow all the time. Some will let students do almost anything most of the time and then block almost everything (IM/IRC/FTP/etc) during exam times. Others change their policy whenever a particular program is being used for abuse and is getting out of hand. The only way to know for sure is to ask them.