Make sure that you're only using 1 software firewall (more than 1 will cause problems) & that LW's being allowed through it. Symantec Antivirus on it's own doesn't include a firewall. But if the Symantec AV is part of a security suite then there might be a firewall included with that. You'd have to check.

There might be a firewall within your modem/router, but we'd need your system details to find that out.

If LW's suddenly stopped connecting, try the advice here: all of a sudden will not connect (a fix to try)
Start off by deleting LW's preferences folder & changing Java versions.
You'll know if you've deleted the preferences folder properly...when you start LW, you'll go through the setup wizard again & all the settings within LW's options will have changed.
If you get confused with deleting the preferences folder, have a look at this post (Windows XP).
One bar, connection problems

Vista users: LimeWire Pref Folder in Vista

If nothing there helps, please give us your details.
System details - help us to help you -> Provide these details when you post!!!