Swing/AWT/SWT :: JButtons Disappearing On Click And Reappearing When Mouseover Occurs

I'm having issues with JButtons and painting methods, whenever I click a grid on the board, the buttons in the JPanel disappear. Here is the board class:

package GUI;
public class Board extends JPanel implements Observer {
/**
*
*/
// private static final long serialVersionUID = 1L;
private final int boardSizeX;
private final int boardSizeY;
private final int L = 20;

[Code] ....

I know the code is messy in places, this will be fixed later, just need some pointers on how to solve the JButton issue.