title: Sandboxed app & NSOpenPanel causes crashes
body: <p>I am doing a simple file open panel in my Cocoa app. I enable entitlements and app sandboxing.
  But on OS X 10.9, when the app should open a dialog using <code>NSOpenPanel</code>, it crashes with:</p>
  
  <blockquote>
    <p>Application Specific Information:<br>
    Terminating app due to uncaught exception 'NSObjectNotAvailableException', reason: 'service com.apple.appkit.xpc.openAndSavePanelService failed to init an instance of NSOpenPanelService on behalf of  due to {
        "proxy-communications-error" = "Error Domain=NSCocoaErrorDomain Code=4099 \"\U041d\U0435 \U0443\U0434\U0430\U043b\U043e\U0441\U044c \U0443\U0441\U0442\U0430\U043d\U043e\U0432\U0438\U0442\U044c \U0441\U0432\U044f\U0437\U044c \U0441 \U043f\U0440\U043e\U0433\U0440\U0430\U043c\U043c\U043e\U0439-\U043f\U043e\U043c\U043e\U0449\U043d\U0438\U043a\U043e\U043c.\" (The connection was invalidated from this process.) UserInfo=0x61000047dc00 {NSDebugDescription=The connection was invalidated from this process.}";
    }'</p>
  </blockquote>
  
  <p>Source:</p>
  
  <pre><code>self.panel = [NSOpenPanel openPanel];
  panel.delegate = self;
  panel.canChooseDirectories = YES;
  panel.canChooseFiles = NO;
  panel.canCreateDirectories = YES;
  panel.allowsMultipleSelection = NO;
  [self.panel beginSheetModalForWindow:contextWindow completionHandler:^(NSInteger returnCode) {
          ...
      }];
  </code></pre>
  
  <p>Has anyone seen this before?</p>