title: Why might a Django admin form hang (or, how can I diagnose the problem)?
body: <p>In Django, I have a model tied to the admin. Whenever I try to add a new model instance, or update an existing one, the form hangs while trying to submit. Nothing is written to the log files, though. The models are nothing fancy, so they don't have any custom validation that may be causing, e.g., and infinite loop. Also, the hang only occurs on my production server, not on the staging server or my local development machine.</p>
  
  <p>I've noticed the following error in the Apache log files, but I'm not sure if it's a symptom of my problem, or something else:</p>
  
  <blockquote>
    <p>Exception exceptions.TypeError: "'NoneType' object is not callable" in > ignored</p>
  </blockquote>
  
  <p>What might be causing the hang? Or, since that's probably hard to answer without all the specifics of my setup and application, what's the best way to diagnose the problem?</p>