Button highlight and Menu lost after Hiding Application

I have an AppleScript Studio app I wrote that works pretty well. The main NIB has three buttons, one highlighted. If I hide the application and then bring it back (click on the icon in the dock), the application comes up but there is no default button highlighted. Also, the menu seems locked.

The buttons are still usable (just no highlight). If I click on a button, the menu becomes accessible again and the button highlight comes back.

So, is there a setting that I need to put to make the application work properly after being hidden?

Thanks,

A.