your problem is the HUB. It cannot route the incoming packets to the proper computer sending the request, causing a collision.
Try this disconnect the hub and connect the comp directly to the dsl modem, then open ZA and go to programs and clear all instances of MSN messenger.
Start up MSN, when ZA pops click to remember and allow to access internet, it should also pop up to allow server, have it remember that too. If it doesnt ask for the server allowance, go to the programs area of ZA and set it to.
It should work now.
IF you have the DSL connected to the hub and the comps to the hub its a wonder your even getting out on the net. You need a router to ROUTE the incoming and outgoing packets to the proper computer.
If by chance you have the DSL connected to a computer and the computer to a hub, using the hub for the other systems to reach the DSL, then you have made the system that IS connected the gateway, therefore your going to have to use a proxy program or ICS. AnalogX has a very simple and good proxy program that you could use