Can you replicate the issue? If so, is it on a specific browser or all browsers. My guess is that is is the java plugin for the browser.
I have had a similar problem and it seemed to be because of the browser, not nanogong. I removed the java plugin from the browser, cleared my cache, closed the browser, than restarted the browser. When I got to the page which requested the jar file, I received a browser warning indicating that java must be enabled, do i want it enabled? I activate and the plugin worked.