Onkeyup event slow in IE - autocomplete search attempt

Onkeyup event slow in IE - autocomplete search attempt

I have setup a keyup event on a textbox that clears a timer every keystroke, and uses the settimeout function to execute an ajax request.   Every browser works great except for IE8 and I am assuming 7.   Every key that you type lags in the textbox, but ajax request functions as expected.   How do I stop the lagging?  I could type 3 letters and they dont show up right away.  I appreciate any advice.

Below is a code example:

  2. //Keypress Function To Block Enter Key
  3. $("#textbox").keyup(function(event){
  4. currentFilter = $(this).val();
  5.  
  6. if (event.which == 13)
  7. {
  8. event.preventDefault();
  9. }
  11. else
  12. {
  14. //Clear Timer When Needed
  16.    clearTimeout(timer);
  17.  
  18.    timer = setTimeout(function(){
  19.    
  20.     searchServer(currentFilter)}, 1000);
  21.  
  22. }
  24. });

  26. function searchServer(currentFilter)
  27. {
  28. var urlString = currentServer + provisionerController + "?" + action + "=" + actionValue + "&" + partnerGroupAction + "=" + selectedAccountGroupText + "&" + filteredTextAction + "=" + currentFilter;
  29. var webSafeUrl = encodeURI(urlString);
  31. $.ajax({
  32.  url: webSafeUrl,
  33.  dataType: "html",
  34.  cache: false,
  35.  type: "POST",
  36.  beforeSend: function(){
  37.  loadingImage.show();
  38.  },
  39.  
  40.  complete: function(){
  41.  loadingImage.hide();
  42.  },
  43.  
  44.  success: function(data){
  45.  accountsTableDataContainer.html(data);
  46.  }
  48. });
  49. }