'Occasionally', I find myself connected behind a restrictive firewall. MSN Messenger, being the best known IM client, are usually first to be blocked. I've been trying a few free solution, and the one that works for my particular situation is "HTTP-Tunnel":http://www.http-tunnel.com + "Gaim":http://sourceforge.net/projects/gaim

"Trillian,":http://www.ceruleanstudios.com "HTTPort,":http://www.htthost.com/ and the official client does not let me through in any combination.