I don't believe that Lord Nick person really was a tester, we hand picked a small group of testers, personally picked by Firefly staff.
Perhaps the firewall may need the ports to be opened, do you have a software and hardware firewall.
Must allow outgoing TCP connections to remote port 6667
Must allow outgoing TCP connections to remote port 28910
Must allow incoming & outgoing traffic via local UDP port 19966
Must allow incoming & outgoing traffic via local UDP port 13139
Our friends over at Stronghold Knights may have some further helpful information for you
http://www.stronghold-knights.com/site/index.php?name=PNphpBB2&file=viewtopic&t=9447