I don't know much if anything about Linux unfortunately. The Actiontech will have an internal firewall. Question is, is the UPnP communicating properly between LW & the device if you are using it in UPnP mode.

It will probably be a good idea to make a note of all your option settings, then delete your LW prefs folder whilst LW is closed, found here I think: ~/.limewire
Else nowadays it might just be called limewire.