IRC ?
it's the oldest chat protocol that has ever been used on the internet !
Not knowing IRC is like, say, not knowing FTP
(no offense meant btw)
I would be VERY surprised that you couldn't do IRC whereas you could do MSN, ICQ or Yahoo chat from the same machine. What you see probably is just the Java applet doesn't work. But you could still use IRC using a normal (non-java) client such as mIRC or the ones we've been talking about here...