>> ALL class libraries are included in the project
>May be just a bad link.
>Did you try to destroy and create a new object in your form?

Do you mean make a change to the form and rebuild the EXE? Even if that would fix the problem, it is impractical to do it to hundreds of forms in tens of applications. It is not one single form, the error may happen in any of our forms. Besides, the error goes away without any change, and comes back...