If it helps anyone - following is the code that I have which I think is working in an ASP.NET MVC app.  This function gets called on a $(document).ready.  Notice that the code checks if the editor 'is ready'.  If not, it is calling the same method again after 10 milliseconds on a 'settimeout' - until it finds the editor is ready.

var responseInitialized = false;

function initializeEditorText() {
       var contentEditable = '<%= repsonseEditable%>';
       if (("" + contentEditable).toLowerCase() == 'true') {

           if (responseInitialized == true) {
               return;
           }
           var editor1 = $(".myEditor");
           if (editor1 != null) {
               if (editor1.length > 0) {
                   if (editor1[0].IsReady && editor1[0].setHTML != null) {

                       setEditorText("" + $("#responseText")[0].value);
                       responseInitialized = true;
                       sizeForm();
                       $('.myEditor').resize(function () { sizeForm(); });
                   }
                   else {
                       alert('will be trying initializeEditorText one more time in 10 milliseconds!');
                       setTimeout(function () { initializeEditorText(); }, 10);
                   }
               }
           }
       }
   }