You are losing the object when closing the form. I would suggest to cancel
FormClosing
events and just
Hide()
the form. So, in
CR_FormClosing
(not
CR_FormClosed
) you would have
e.Cancel = true;
CR.Hide();
and then in
CreateToolStripMenuItem_Click
you would have
if (CR == null)
CR = new CreateDB.Form2();
CR.Show();
This way you create the form only once, and then just hide/show it when necessary.