I also use a mac & I know little about networks. So I didn't even notice any tone, etc. lol

At least that's good news that the port isn't blocked.

You could try forcing ip within LW: Force IP instructions & sample image

You could also try manually connecting. ie: Open LW & change the settings. Tools>Options>Connections & untick the option & press Apply. Then close LW down & re-open. Leave it for a time, then manually connect it by going to File>Connect

Otherwise perhaps try the new beta 4.3.3 which overcomes some bugs in LW 4.2.x : http://www.limewire.com/english/content/beta.shtml or at the bottom of your personal downld page if you're a pro user.