Java webstart – absence of errors, absence of forms

This one is beautiful. If you get an unhandled run-time exception in the public void main(String args[]) method then your application simply won’t launch. You should make sure to intercept all exceptions in the main class and then throw up a simple error dialog.
Of course this doesn’t work if you are missing a class in the distribution, the exception happens before you get to the main method.
Quick tip: enable and show the java console (JavaCPL on linux, java control panel under windows) it’s under Java console in the Advanced tab.