os/x 10.5 (leopard), oXygen-9.0.0 (eclipse-3.3.1.1 plugin), xep-4.1

New to Mac; following error with attempting to execute XEP from oXygen:

[XEP FO processor] The process 'XEP FO processor' ended with code: 1. The error was:

Exception in thread "main" java.lang.NoClassDefFoundError: com/renderx/xep/XSLDriver

Help please.

Ray