JToolbar Buttons too large in Ubuntu 7.04 when using native look and feel

After upgrading to Ubuntu 7.04, Toolbars in Java Swing Applications don't display correctly when using NATIVE Look and feel.
The buttons are too large and also when adding text and combo boxes, they are much too big.

Steps to reproduce:

Create a Java Swing Application, set NATIVE look and feel:

 UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());

create a JFrame with a JToolbar

In Ubuntu 6.10 everythings was displayed fine, after upgrading to 7.04, it all got messed up on both of my pc's.
(1 clean install and 1 upgrade, same behaviour)