Painting on a JPanel - HELP!

I have overridden the following method with:

protected void paintComponent(Graphics g)
{
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        JigsawPiece tmp;

        while (hasNext())
        {
            tmp = nextJigsawPiece();
            g2.drawImage(tmp.getPartialImage(), tmp.getRelativeXCoord(),
tmp.getRelativeYCoord(), this);
        }
}

When I load my program, nothing appears. I go to resize the window and the
image appears, I move or resize the window again and it dissappears.

Pleeease help me,
Graham.