Floating Dialog Panels Display Incorrectly in 2.6.3

I just upgraded to 2.6.3. The new floating dialog panels have problems with their height. For example, I have a plugin that uses the following code:

FCKCommands.RegisterCommand(
   'YouTube',
   new FCKDialogCommand(
      'YouTube',
      'Add Video',
      YouTubeURL,
      450,
      370
   )
);