Help - Header squished if vertical scrolling is enabled

I've tried everything I could think of - upgrading to 1.9.2 (Using 1.9.0 right now), changing options - I just can't seem to fix the headers squishing down when the page is loaded, if vertical scrolling is enabled. Without it, it loads fine. Sorting the table after the page loads also works fine. Here's my code:

<script type="text/javascript">
    $(document).ready(function () {
        oTable = $('#tblportVolMiniPositions').dataTable({
            "bProcessing": true,
            "fnStateLoadCallback": function (oSettings, oData) {
                oData.sFilter = "";
                return true;
            },
            "bScrollAutoCss": true,
            "sScrollY": "450px",
            "bPaginate": false,
            "bAutoWidth": true,
            "bJQueryUI": true,
            "aaSorting": [[1, "asc"]],
            "fnInitComplete": function () {
                this.fnAdjustColumnSizing(true);
            },
            "oLanguage": {
                "sSearch": "Filter Records:",
                "sLengthMenu": "Display _MENU_ records per page",
                "sZeroRecords": "No Records found.",
                "sInfo": "Showing _START_ to _END_ of _TOTAL_ records",
                "sInfoEmpty": "",
                "sInfoFiltered": "(filtered from _MAX_ total records)"
            },
            "sDom": 'R<fr>t<"F"ip>l',
            "oColVis": {
                "aiExclude": [0, 1, 2, 3]
            },
            "aoColumnDefs": [
			{ "bSortable": false, "aTargets": ["nosort"] },
			{ "bVisible": false, "aTargets": ["hiddenCol"] },
			{ "bSearchable": false, "aTargets": ["nosearch"] },
			{ "sType": "html", "aTargets": ["htmlData"] },
			{ "sType": "date", "aTargets": ["dateData"] },
			{ "sType": "string", "aTargets": ["textData"] },
			{ "sType": "numeric", "aTargets": ["numberData"] },
			{ "sWidth": "25px", "aTargets": ["smallCell"] }
            ]
        });
        $(window).bind('resize', function () {
            oTable.fnAdjustColumnSizing();
        });
    });
</script>

<table name="tblportVolMiniPositions" id="tblportVolMiniPositions" class="normal display" style="border-collapse:collapse;width:100%;">
	<thead>
		<tr>...

The page is loaded dynamically via AJAX, so it probably has something to do with how it's initially loaded. Here's an image of what it looks like when the page first loads: http://i.imgur.com/kbVkS.png