the parameters are reversed.
try:
default:
$rsProducts = new WA_MySQLi_RS("rsProducts",$ecartdb,0);
$rsProducts->setQuery("SELECT products.*, categories.* FROM products INNER JOIN categories ON products.ProductCategoryID = categories.CategoryID WHERE (categories.CategoryLink = ? OR -1 = ?) AND categories.CategoryLocation = ?");
$rsProducts->bindParam("s", "".(isset($_GET['Category'])?$_GET['Category']:"") ."", "-1"); //WAQB_Param1
$rsProducts->bindParam("s", "".(isset($_GET['Category'])?$_GET['Category']:"") ."", "-1"); //WAQB_Param2
$rsProducts->bindParam("s", "".(isset($_GET['Department'])?$_GET['Department']:"") ."", "-1"); //WAQB_Param3
$rsProducts->execute();
break;