Windows Forms user control layout issues at runtime

I'm hoping the good folls of this community can help me figure out what's going on with a Windows Forms user control that I created and am trying to use.

I created a user control that represents a single band of a parametric equalizer.  In the designer, the control looks like this:

 When I debug the control in the Test Container, things look good:

If we take a look at the actual PEQ application that will use the control, things still look OK in the designer:

It's only when I fire up the application that things go... awry:

What happened to all the TextBoxes?  And the ComboBoxes?  I''ve got a feeling that the fix for this is something really simple, and I'm going to feel like a complete idiot for not figuring out the obvious.

Can anyone tell me what my dumb self did wrong?