in the admin/scripts/products_results.js file, change line 29
var thepage = "Update_ProductCoupons.php?Add=1&ProdID="+ProdID+"&GroupID="+GroupID;
to:
var thepage = "update_productcoupons.php?Add=1&ProdID="+ProdID+"&GroupID="+GroupID;
and line 33
var thepage = "Update_ProductCoupons.php?ProdID="+ProdID+"&GroupID="+GroupID;
to:
var thepage = "update_productcoupons.php?ProdID="+ProdID+"&GroupID="+GroupID;