This seems like yet another bug in Install Anywhere.

Make sure you have lax.jar in your LimeWire install folder.

Then edit LimeWire.lax and look at the line 'lax.class.path='. Ensure that lax.jar is in the colon-separated list of .jar files, and if it is not, enter it. My lax.class.path looks like this, and probably you will not go far wrong if you copy it (at the very least, it might change your error message :->)
lax.class.path=RunLime.jar:swing.jar:jl011.jar:Lim eWire.jar:collections.jar:xerces.jar:MessagesBundl es.jar:lax.jar

Good luck