I'd recommend getting the latest code from CVS. The last time I checked the zips, the code was from months ago.

LimeWire usually comes with a collections.jar file that has the collections classes. If you look at the compile batch files/shell scripts in the core and gui directories, you can see how the classpath is set. You should also be using ant to build LimeWire. Be sure to follow the instructions for installing ant.

Links:
http://www.cvsgui.org/
http://jakarta.apache.org/ant/index.html