Scrolling breaking when I add arguments into the array

Hello,
Since this is my first post I'd just like to mention what a great plug-in datatables is..so well documented.
I am having an issue with the scrolling parameters. When I add a DOM positioning parameter into the array all scrolling becomes disabled.

Here is the custom script I attempting to use:

$(document).ready( function() {
  var oTable = $('#ad_table').dataTable( {
      // "sDom": '<"hidden"i>',
      "aoColumnDefs": [
        { "sType": "numeric", "aTargets": [2,4,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31] },
        { "aDataSort": [ 5, 6 ], "aTargets": [ 5 ] },
        { "aDataSort": [ 3, 6 ], "aTargets": [ 3 ] },
        { "aDataSort": [ 1, 6 ], "aTargets": [ 1 ] },
        { "bSearchable": false, "aTargets": [1,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31] },
        { "bVisible": false, "aTargets": [2,3,5] },
        { "sWidth": "40px", "aTargets": [0] },
        { "sWidth": "20px", "aTargets": [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31] },
      ],
      "bScrollCollapse": true,
      "sScrollY": "200px",
      "sScrollX": "100%",
      "bPaginate": false,
  });

  oTable.fnSort([[6,'asc']]);
  new FixedColumns(oTable);
});

https://github.com/justinshea/TableDemo-v2

You will notice that the "sDOM" argument is commented out. When it is not commented out the information element is placed into a div with class of "hidden" as intended. But, if it is not commented out then the scrolling also becomes disabled. Can someone please help me troubleshoot? Is this a bug or have I not constructed the array properly?

Thanks,
Justin