[jQuery] jQuery SlideDown and SlideUp Problem

[pedramphp]

int my Firefox Browser which is versian 2.1.14 the latest versian of
the 2 ...
if the content Scrolls down in the page to the Bottom of the page then
if we do some slideDown or slideUp Effect the page starts to Flash for
a second ... but I don't have this Problem IN the IE 7
...
so what is the solution

this is my code ... I did some Paging stuff with jQuery


/****************************Down Paging starts
***************************/
$("table#downProPaging span a").click(function(){
  var PagingData={
        start:$(this).parent().attr("id"),
        bId:$("#DownDataPostBid").val()
  };
  $.ajax({
    url: 'pro/showpro/DownData.php',
    type: 'POST',
    data: PagingData,// id of the tree
    dataType: 'html',
    cache: false,
    beforeSend: function() {
      $("#showProDownMsg:visible").hide();
          $("#down_in_data_pro").slideUp(1000);
          $("#down_in_loading_pro").show(1000);
      $("#down_in_loading_pro").html(inimg);
    },
    error: function(){ // if the data has not been send
          alert('xml error');
    },
    success: function (txt){
          $("#down_in_loading_pro").hide(1000);
          $("#down_in_data_pro").html(txt);
          $("#down_in_data_pro").slideDown(1000);

    }
  });
  return false;
});

/****************************Down Paging Ends
***************************/
Regards Pedram