MDI parent disappears when showing modal form

[ASMA]

Hi everybody

I´m working with an MDI form, but from time to time I need to show a modal (SDI of course) form.

The problem comes when I close that modal form. MDI parent form vanishes during one second showing all forms behind it, making a horrible effect.

I´ve tried to hide it first but it still does not work

Any suggestion?

Thank you in advance