[jQuery] form plugin and blockUI problems in IE7 with the ui not unblocking

[tradeallday]

I'm using the form plugin and the most recent version of blockUI.

Here's my form initialization area:

                $(document).ready(function() {
                    var options = {
                        target:        '#search_results',   // target 
element(s) to
be updated with server response
                        beforeSubmit:  showRequest,  // pre-submit callback
                        success:       showResponse  // post-submit callback

                    };

                    // bind to the form's submit event
                    $('#search_form').submit(function() {
                                $.blockUI();
                        $(this).ajaxSubmit(options);
                        return false;
                    });
                });


And then here is my post submit callback function

                // post-submit callback
                function showResponse(responseText, statusText)  {

                        // add sorter.
                        $("#myTable").tablesorter({sortList:[[0,0],[2,1]], 
widgets:
['zebra']});
                        $("#options").tablesorter({sortList: [[0,0]], headers: 
{ 3:{sorter:
false}, 4:{sorter: false}}});

                        // add pager.
                        $("#myTable").tablesorterPager({container: 
$("#pager")});
                        $("#pager").show();

                        $.unblockUI();
                }

All this works ok in Firefox but in IE, blockUI does not unblock. I
don't get any javascript errors and it seems like the call should go
through ok. Any ideas?

Thanks,