MVC3 Unobtrusive Validation Not Working after Ajax Call

$.validator.unobtrusive.parse("#frmAddItem"); will work. Do note that it must be in the partial that you load through ajax (below the form in the partial)

<form id="frmAddItem" method="POST" action="...">
    <!-- all the items -->
</form>
<script type="text/javascript">
    $.validator.unobtrusive.parse("#frmAddItem");
</script>