Putting updated Xerces, Xalan, and JAXP JAR files from the Java XML Pack Summer 02 Release in the Java 1.4 Endorsed Standards Override folder breaks LimeWire. The only solution is to remove the JARs from the folder. Apparently, LimeWire requires Xerces 1.x, and there are classloader problems between the endorsed directory and the LimeWire Xerces 1 on the classpath.