Hi Cimteker,
You as the user specify what happens when you click the X button on the panel. If you double-click on your panel, you will notice an option called Close Control. Whatever callbcack you specify here is where the EVENT_COMMIT event is sent to. Typically you set that option to a quit button's callback. That quit button should call QuitUserInterface.
Essentially you just have to call QuitUserInterface before doing unloading your DLL. If you unload that DLL before doing anything with your UI, your putting CVI into an unstable state.
After you have closed the UI and you have returned back to your main application, the test executive, then you should call FreeLibrary on your DLL.
Best Regards,
Jonathan N.
National Instruments
