^^^ What Lillu said

EQ also uses a ton of different ports for zoning, chat channel, world server, etc. A few years ago I suddenly out of the blue started crashing while zoning 99% of the time, and was totally unable to keep chat channels up. Turns out my isp suddenly started routing traffic every which direction, and blocked a variety of ports. Had to connect to EQ through a VPN in order to properly zone/stay connected. Did this on live EQ and all eqemu servers.
Note that if you insta crash to character select (like superhoss asked), it's due to MQ2 messing up by doing something like trying to cast one thing while moving another item and casting something else, etc.