Griffon & Gsql plugin error

I am new to griffon, and am trying to get somethings working on it. When I run the command install-plugin 开发者_如何学Gogsql, and then run-app or test-app, my griffon application, I get noClassDefFoundError "Lgriffon/Core/GriffonApplication". The error occurs only after I install the plugin. I have no idea why is it there. Any help appreciated, thanx