>>>>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.
>
>Interesting. How sure are you that the ON SHUTDOWN is still active? i.e. do you have any ON SHUTDOWN's without the optional clauses that might be accidentally releasing the ON SHUTDOWN? Or, are you sure that the ON SHUTDOWN did not fire - is it possible that it did fire, but returned prematurely (can you post the code in your ON SHUTDOWN routine)?
>
>The only other thing that springs to mind is a dangling reference - if this to a form then it would generally prevent the form from being released, but this also generally results in the form remaining visible - so this seems less likely.

I just ran a test to confirm whether ON SHUTDOWN was still active or not after the preference values is saved. Indeed, it was no longer active. I'll dig in further and find the source.

Thank you for your help!