Index: administrator/components/com_virtuemart/plugins/vmpsplugin.php
===================================================================
--- administrator/components/com_virtuemart/plugins/vmpsplugin.php	(revision 7068)
+++ administrator/components/com_virtuemart/plugins/vmpsplugin.php	(working copy)
@@ -959,12 +959,22 @@
 			$db->setQuery ($q);
 			$taxrules = $db->loadAssocList ();
 		} else {
+			
 			//This construction makes trouble, if there are products with different vats in the cart
 			//on the other side, it is very unlikely to have different vats in the cart and simultan it is not possible to use a fixed tax rule for the shipment
+			if (empty($cart_prices[$this->_psType . 'Value'])) 
+			{
+			$cart_prices['salesPrice' . $_psType] = 0;
+			$cart_prices[$this->_psType . 'Tax'] = 0;
+			$cart_prices[$this->_psType . '_calc_id'] = 0;
+			return; 
+			}
 			if(!empty($calculator->_cartData['VatTax']) and count ($calculator->_cartData['VatTax']) == 1){
 				$taxrules = $calculator->_cartData['VatTax'];
+				//var_dump($taxrules); die(); 
 				foreach($taxrules as &$rule){
-					$rule['subTotal'] = $cart_prices[$this->_psType . 'Value'];
+					$rule['subTotal'] += $cart_prices[$this->_psType . 'Value'];
+					break; 
 				}
 
 			} else {
@@ -975,6 +985,7 @@
 			}
 		}
 		
+		
 		if (count ($taxrules) > 0) {
 
 			$cart_prices['salesPrice' . $_psType] = $calculator->roundInternal ($calculator->executeCalculation ($taxrules, $cart_prices[$this->_psType . 'Value'],false,false), 'salesPrice');