Trouble with JFrame Sizes, background always seem to be exposed

Question

I must be misunderstanding how this pack() and setPreferredSize() thing works. Basically I have a JPanel, which I draw a blue background in. I set it up so that it is a gridLayout.
super(new GridLayout(GRID_ROWS, GRID_COLS, GRID_SPACE, GRID_SPACE));
setPreferredSize(new Dimension(GRID_COLS * CELL_SIZE,GRID_ROWS * CELL_SIZE));to me this means I have a gridlayout of squares.
then I add JLabel "blocks" to this gridlayout, so that it will look like a maze. I set the preferred size of the JLabels to CELL_SIZE. So I would think everything would fit nicely. Then I insert this JPanel onto a JFrame. I also add another JPanel (ButtonPanel) to the bottom of the JFrame, and this seems to screw everything up.
First off, am I doing this setPreferredSize() stuff right. I was under the impression that I should set the preferredSize() of all the subcomponents, and then on the larger component, one that I really don't have a preferredSize() for, I just pack() it, and that will shape around the limitation of the subcomponents.
Secondly why doesn't this ButtonPanel just scale to the size of the maze? Why does it have to stretch it out, so that my, once square looking JLable blocks, look like rectangles? Is there a way short of setting the PreferredSize(some_number_of_pixels), that is more elegant that will make the ButtonPanel behave?

Answer 1

No takers? really any ideas about why this might be please let me know. I have a feeling it is a somewhat simple concept, but I'm just missing the point or something.