CAPI method on window close or quit

I have successfully delivered a capi application making use of  
objective-C and framework modules.
The interface is relatively simple, only buttons on a window. I did  
not implement any items on the menu bar, the basic options provided by  
CAPI were fine with me.

However, is some occasions, my application freezes when the main  
window is closed or when I quit the application. I used the :quit-when- 
no-windows delivery key but that does not change the behaviour.

I think I need to do some house cleaning prior to quitting the  
application. Should I implement my own menu bar then? Or is there a  
quick way to specialized the quit method without having to add the  
menu bar explicitly in my capi interface?

Thanks

Bruno