Is there a known bug in calling one Modal Form from another?

What is happening is that if I am on one modal form, then call another modal form, when it releases my first form is no longer acting as modal (ie can get to menus etc)
I dont know if this is a bug or something in my code/base classes.
Ive tried putting

ThisForm.Hide()
*Do other form
ThisForm.show(1)

but it didnt help. Ive checked with the debugger and the forms WindowType is still set to Modal.

anyone have this problem before?