Don't use the Windows & Norton firewalls together, they'll conflict
Turn off the Win firewall & configure the Norton to allow LW.

What's the model of your SpeedTouch?

Have you only had connection problems since updating to 4.16.2 or did you have the same problem with earlier versions?

Have you been through this thread (I guess you have, since you said that you'd tried all correction methods)?
If LW Will Not Connect

When you deleted LW's preferences folder & replaced the gnutella.net file, did you make sure that LW was completely closed first (check in Task Manager)? Did you also look for a preferences folder in the old location (.limewire)? Did you restart your computer afterwards?

When you tried other Java versions, did you make sure to remove any versions currently installed on your computer, before installing another version?

Have you tried port forwarding for your router?