You're not looking for a folder called 'preferences' are you? The prefs folder within Application Data is called LimeWire. You don't have to open that folder, just delete it.

If you're connecting with a router or modem-router, it probably has an internal firewall. If you want to address the firewall issue, please tell us the brand & model of your modem/router.

Did you try reinstalling the older Java?

Have installed the old Java as you said,
Am using the standard cable modem 351000 from NTL,
nothing has been changed since Limewire last worked, used Limewire for a few years,
seems everyone is getting the same problem, so there must be a common factor.

There's not much info about that modem but it doesn't seem to have a firewall. Do you have a router as well?

Did you successfully delete that preferences folder? You'll know if you did...all your LW options would've reset to defaults.

Which other port did you try? Try 64049, or something else in the range of 49152 - 65535.