paolini what's changed since it was working? And what have you tried? It might sound very basic, but try deleting your LW Preferences folder whilst LW is closed; instructions here: Point #2 in Fixes for Limewire (sample at bottom of page.)

What modem/router device brand name & model number do you have. See if it has a UPnP (Universal Plug & Play) switch on the outside. If you know how to log into the device using your browser, check to see if there's a UPnP option. If yes, enable it.