Firstly i would like to say i haven't got a clue what i am doing and the answer to this question is probably really easy

I have been using the wl-500g for a few days now, but since i have been using it my file transfer rate on MSN messenger has dropped really far.
MSN advised me to:

Open as many TCP ports as you can between 6891 and 6900.
Configure the TCP ports so that sockets on a port remain open for an extended period of time.

How do I do this?
And could it have anything to do with the firewall?

thanks