Firstly, if you remember what it was you changed, simply change it back. Make sure you have port 6667 open, and preferably port 6667-7000 - you can only connect to the ports you have open and which are configured with the server (port 6667 is open for just about every server on IRC).
Secondly, if there is a "Reset" or "Reset defaults" button with that Firewall, click it, then try to connect. If not, then only if you know how
you can always try reinstalling the Firewall completely - there should be help files with that Firewall given the manufacturer, and that should have instructions on how to reinstall (or uninstall -> install).
You can also click here
for a technical explanation of that error message.
A Search of the Forums will not do too much good I'm afraid, there have not been too many people with that error message (thought that might save you a little time).
Good luck, hope you get connected, and happy chatting