title: Int fields becoming inaccesible, after first click-in, in Traits/UI GUI
body: <p>I have a Enthought Traits/UI GUI application with several <em>Int</em> traits.
  I find that all of these allow me only one access, after program start.
  That is, I click in one of them and am allowed to edit the value, but just once.
  The next time I try to click on the Int, it's unresponsive and I can no longer edit the value.</p>