1) Click on "Tools" at the top of your screen, and then click "Settings" on the drop down menu. This is where you can configure all of your LimeWire settings. It is alternatively called the Configuration window.

2) On the options/configuration window, click on the network tab. Here, there is a section called "Listening Port." The default number for this is 6346. If it is not, change it.

Also, there could be a slight possibility that LimeWire is unable to find your internet connection. On this same window, make sure that your "Connection Speed" is set to "Cable/DSL."

Hope this helps! :-)