they did not address your question.
they are talking about connecting to a regular ftp port(also called control connection). you have no problems with that, since you can login to the site just fine.
you are having problem with DATA connection port.
here's basic explanation of how ftp works
http://slacksite.com/other/ftp.html
but they did bring up one possibility that your ISP maybe causing this issue.
if you can, connect your computer to another ISP and see if that makes any difference.
also try to temporary disable norton's firewall. make sure it's completly disabled(ie all related services are stopped and stuff). and see if that makes any difference too.