Try

ON SHUTDOWN QUIT

John

>>>In my application, when the users changes values in the system preference and saves it, I release relevent forms and reload them.
>>>
>>>The problem is that if the user click on the X at the upper right corner of the main application window, he/she gets a message window titled " Microsoft Visual Foxpro" and the message says "Cannot Quit Visual Foxpro".
>>>
>>>Does anybody know what would cause the message to be issued?
>>>
>>>TIA
>>
>>You need to add an

ON SHUTDOWN DO MyFunction()

to your main.prg
>
>I already have that. This occurs prior to On ShutDown.