How to deal with orientation change with a ProgressDialog showing?

I am showing a ProgressDialog in the onPreExecute method of an AsyncTask object and canceling the ProgressDialog in the onPostExecute method. In the doInBackground method I am making an HTTP request for user registration. I wish to allow screen orientation changes. When I change the orientation while the doInBackground method is still running, i get all sorts of fun errors like 'IllegalArgumentException: View not attached to window manager' and 'RegisterScreen has leaked window...'

How can I properly continue to show the ProgressDialog after an orientation change? Or maybe, how can I disable orientation change after the user requests to submit their registration?