subview bindings not working in NSBox with bound hidden attribute

[rhoge at nmr.mgh.harvard.edu (Rick Hoge)]

I'm trying to toggle the visibility of part of my user interface by 
making the elements I want to show or hide subviews of an NSBox and 
binding the hidden attribute of the box to a display attribute 
maintained by the window controller.  This works in that the box and 
its subviews have their visibility toggled as expected, but the 
subviews (NSImageViews with values bound to NSImage instance variables) 
don't have any content.  All the subviews and their bindings work fine 
if the hidden attribute of the superview (the box) is not bound.

Any ideas on what might be going on here?  I want to achieve something 
like the functionality in iCal where you can toggle visibility of the 
To-Do list.  Is this a reasonable way of doing this?  I also 
substituted an NSView for the NSBox and got the same problem.

Thanks for any suggestions,

Rick