When LimeWire is not running, open your the file called "limewire.props" in your LimeWire installation directory in a simple text editor.

As mentioned in an earlier post, you should see a line that reads:

MAIN_CLASS=a.a.a.b.Main

Change this line to read:

MAIN_CLASS=com.limegroup.gnutella.gui.Main

and then save the file.

The next time you run LimeWire, everything should work correctly.