Ah, I see the problem. You're trying to set the Title before the window has been realized. In other words, the setTitle() public method tries to retrieve the current window by calling the JIDE methods and those methods must be accessing the peer component -- which doesn't exist yet. It's probably getFormContainer() that's returning null.
In general, public methods shouldn't be called by constructors because of exactly this problem. The constructor's job is to initialize the object and by definition public methods expect the object to already be initialized. Catch-22.
I understand what you're saying, but I don't think that is the problem. While setTitle() is being called on an object that hasn't been fully initialized, the method that is throwing the exception is called on a fully
Besides, the peer component doesn't get created until the setVisible() method is called. If that was the problem it would happen each and every time the code was executed, not just when loading from WebStart on some computers. Judging by the exception all of this code is executing on the AWT Event Thread, so it isn't something like an invokeLater() problem either. That doesn't mean that the Abeille doesn't load stuff in another thread...