I try to move a part of the program to a separate module. I create an empty module - OK. I move one form, number 6, to this module - OK. I try to edit form2 on the main part and get this error : "Length cannot be less than zero", without even showing the form. what is wrong ? see attached error message. Edit: In addition, at least two controls, opendialog1 and opendialog2, disappeared from the controls list immediately after moving the form, and present an error when compiling. Edit: now I see that when I move form6 to the new module, I also loose forms 2 and 4 from the total of 9 forms. the dialogs were in 4. If I move form 5 instead of 6, other forms are missing ... It looks like something to do with the size of this program (which is quite large).