title: Certain key equivalents cannot be used for NSMenuItem
body: <p>I have an <code>NSMenuItem</code> for which I would like to use the key equivalent Command-Option-C. However, when I set the key equivalent in IB, it does not get associated with the menu item when the app is actually run. The entry has no visible key equivalent, and that command does not invoke the item. Other key equivalents, like Shift-Control-C, do indeed work. The one I am trying to use does not conflict with any other key equivalent in the app. </p>
  
  <p>What could be causing this seemingly random problem?</p>