on the results page, change:
$WADbSearch1->keywordComparison($KeyArr1,"".((isset($_POST["S_ProductName"]))?$_POST["S_ProductName"]:"") ."","OR","Includes","%20AND%20","%20OR%20","%22","%22",0);
to:
$WADbSearch1->keywordComparison($KeyArr1,"".((isset($_GET["S_ProductName"]))?$_GET["S_ProductName"]:"") ."","OR","Includes","%20AND%20","%20OR%20","%22","%22",0);