Cut'n'Paste doesn't work in the 1.3.1 version of Java (which is installed by default with LimeWire). Go to the LimeWire download page and you'll find a link to the Sun Java download pages.

Download Java 1.4.1 (I think Sun call it the JRE2 or something similar) and install it. You should then re-install LimeWire if you are running a version prior to 2.6.3.

Mark