title: IE tries to download json response while submitting jQuery multipart form data containing file
body: <p>I'm trying to submit a form with a <code>file</code> field in it via jQuery.Form plugin, here's the code:</p>
  
  <pre><code>$('form').ajaxSubmit({
    url: "/path",
    dataType: "json",
    contentType: "multipart/form-data"
  ...
  </code></pre>
  
  <p>The server then returns json as a response. Works great in all browsers except IE, which tries to download the response as a file. If I remove the file field from the form, it also works just fine.</p>
  
  <p>I've seen various solutions here and in Google and basically tried almost everything described, including setting <code>enctype</code> for the form via jQuery, but it didn't work.</p>
  
  <p>Any suggestions would be very welcomed.</p>