Perceive

AOL patents Instant Messaging

MSNBC has an article on the whole thing. The patent, filed January 27, 1997. There are 202 claims, which makes this an unbelievably detailed patent, and nearly uninforcable, since most of these claims will not be fulfilled by any given product. I'd wager to sya that ICQ doesn't even fulfill all of them anymore.

it also seems to me that IRC is an excellent example of prior art in this area, although it also doesn't fill all of the claims.