IDE :: Cannot Exit Form After Updating DataGridViewComboBox Cell

The form opens a simple form to accept a password if a name is selected from a dropdown. The form is opened modally from the validating event. If I select an item, fill in the password, close the modal form , it will not let the parent form close depending on how I exit the dropdown. When I look at the closing event cancel is set to true implying that the control still thinks it needs vaidating.

It works if i leave the dropdown cell in focus when I hit close.

If I click (even just once so the dropdown still is highlighted but just closed) on another cell in the grid the form will not close. It corrects itself if I repeats the first method.

Even worse if I press enter twice it crashes without going through any of my code when the grid tries to do its own commit edit on the editableControl but seems to have a wrong reference as it tries to use the DataGridViewComboBox as the editablecontrol and gets a cannot cast exception

Updated as I have found the cause.

The pop up password form is a home brewed modal form by disabling all open forms but leaves some menu items active.(mdi is used). It is the disable form that causes the issue. Without that it always works. So it seems the grid cant handle being disabled while changing cells.

A solution that works is to use ShowDialog but that changes the systems behaviour so I may not be allowed to do that.