I don't really know anything about firewalls, but these links might help you out. If you have any paperwork that came with the software, it might be helpful to dig those out and see if it gives any instructions.
How to manually open Telus ports:
http://kb.telus.freedom.net/index.php?ToDo=view&Frame=1&questId=602&catId=24
Network ports used by Xbox Live:
http://support.xbox.com/support/en/us/xbox360/kb.aspx?id=908874&lcid=1033&category=xboxlive
I assume if you can open those ports it should make Xbox Live usable.