ACCESS '97: Why?: Form Freezes up when setting ListBox default [RESOLVED]

[Webtest]

Esteemed Forum Participants and Lurkers:
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ACCESS '97

Why is it that when I include the following code, it freezes up my panel?

I have some buttons, checkboxes, and a list box that can be operated normally, except that EVERYTHING freezes up when the following is UNcommented:

Private Sub Form_Open(Cancel As Integer)
        'Controls("cmd_DateRange").Selected(0) = True
End Sub

Note that the Form can still be moved and closed, and the proper item in the list box is selected, but all of the controls on the form are frozen.