I am having the same isssue as expressed above. I had everything working fine yesterday and was able to upload images but suddenly today it stopped working and I am also getting Error 2.  I changed the way I am initializing the editor according to your instructions but with no luck.

Here is the initalization code in the controller:

            Editor Editor1 = PrepairEditor(delegate (Editor editor)

            {

                editor.ID = editor.Name = "Editor1";

                editor.Height = Unit.Pixel(400);

                editor.Text = "Type here";

                editor.Skin = "officexpsilver";

                editor.Toolbar = "minimal";

            });

            ViewBag.Editor = Editor1.MvcGetString();

And here is where it is called in my view:

I have wasted hours today trying to figure out what happened and I really need your help. Thanks in advance! 

        <div class="form-group">

            @Html.LabelFor(model => model.PostContent, htmlAttributes: new { @class = "control-label col-md-2" })

            <div class="col-md-10">

                @Html.Raw(ViewBag.Editor)

            </div>