If I understand correctly, all your forms are created with NEWOBJECT/CREATEOBJECT. That means that you store the reference to the form object somewhere. Do you have a form manager? If so, it should be notified when a form is closed so that it can NULLify the reference to that form. Otherwise, make sure that all references to the form are cleared. You may have this error because the form object are not completly released.

HTH

>Since we are in this classes topics, I like to know what is the best way to close my application form created using classes only?
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>My application give 'Too many open windows' when user close and open different form through the menu. My user just click the x button to close the form class.