Node.js has stopped uploading

I'm at a loss, recently my express 4 app has stopped uploading. Any attempts to upload a file result in 'Uploading: 0%' and it just hangs there and none of the events below fire so I can't even get an error.

router.post('/uploader', function(req, res){
  var form,realFileName;
  form = formidable.IncomingForm();
  form.uploadDir = path.join(__dirname, '../' + opts.uploadDir);
  form.maxFieldsSize = 1000 * 1024 * 1024;
  form.keepExtensions = true;
  form.type = 'multipart';

  form.on('fileBegin', function(err, file){
    file.path = form.uploadDir + "/" + file.name;
    realFileName = file.name;
  });

  form.on('file',function(name, file){
  });

  form.on('error', function(err){
    res.render('uploader',{title: 'Upload Error'});
  });

  form.on('end', function (err, file){
    res.render('uploader',{title: 'Upload Success'});
  });
//res.render('uploader',{title: 'Upload Success'});
});

Form:

<form action="/uploader" method="post" enctype="multipart/form-data">
  <input type="hidden" name="MAX_FILE_SIZE" value="104857600">
  <input type="file" name="uploadCsv">
  <input type="submit" value="Upload CSV">
</form>

You need to call form.parse(req); after you set up the events:

form.on('end', function (err, file){
  res.render('uploader', {title: 'Upload Success'});
});

// --> Missing: "Start parsing the form":
form.parse(req);

See Formidable's example for a full example.