button onAction issue on Mac

If I would like to execute an onAction function on a button (active by elements.button.requestFocus()) on a form in Smart Client by the return and/or enter key it doesn’t work on my Mac’s (iMac + MacBook pro). It only works by a mouseclick.
I guess the issue is since I have installed the Java version 1.6.0_24 on Mac. The issue occurs only on Mac.
Any ideas how I could fix that?

Mac OS X 10.6.7
Servoy 5.2.6 / 5.2.7

Regards
Thomas