OH those ports for MSN Messenger probally wont work!
here is a snipit of how Windows Messenger works behind a NAT
"Microsoft has implemented the Universal Plug and Play (UPnP) protocols in Windows XP, but that will only work if the NAT device also implements the UPnP protocol. (Without this support, voice and video using Windows Messenger will not work reliably behind a NAT device)."
here is a link to what you need to know looks like it is supposed to open necessary ports Automatically, provided your router implements the UPnP Protocol:
http://www.microsoft.com/windowsxp/using/windowsmessenger/expert/bowman_december24.mspx Good Luck!!