Please help with a MS SQL Select query (calculate total order weight)

I have the following query:

SELECT O.OrderID
     , O.ShipFirstName
     , O.ShipLastName
     , O.ShipCompanyName
     , O.ShipAddress1
     , O.ShipAddress2
     , O.ShipCity
     , O.ShipState
     , O.ShipPostalCode
     , CT.Name AS Country
     , O.ShipPhoneNumber
     , O.ShippingMethodID
     , O.TotalShippingCost
     , (O.PaymentAmount - O.TotalShippingCost) AS FOB
     , O.OrderStatus
     , O.BatchNumber
     , O.Custom_Field_eBayID
     , C.EmailAddress
     , od_totals.Product_Count
     , od_totals.Order_Weight

FROM Orders o
JOIN Customers C ON C.CustomerID = O.CustomerID
LEFT JOIN Countries CT ON CT.Name = O.ShipCountry
INNER JOIN (
    SELECT od.OrderID
         , COUNT(DISTINCT od.ProductCode) AS Product_Count
         , SUM(od.Quantity * p.ProductWeight) AS Order_Weight
    FROM OrderDetails od
    INNER JOIN Products_Joined p ON p.ProductCode = od.ProductCode
    GROUP BY od.OrderID
    HAVING MAX(CASE WHEN od.QtyOnBackOrder > 0 THEN 1 ELSE 0 END) = 0
) AS od_totals ON od_totals.OrderID = o.OrderID

WHERE o.ShipDate IS NULL
  AND o.BatchNumber IS NULL 
  AND (
      o.OrderStatus = 'PROCESSING'
      OR (
      ShippingMethodID = 6761
      AND BatchNumber IS NULL   
      AND OrderStatus <> 'CANCELLED'))
ORDER BY O.OrderID ASC
;

Select allOpen in new window

The problem seems to be in lines 27 and 28. I've done something wrong here.

You'll notice that there are some calculated fields, included these two:
     od_totals.Product_Count
     od_totals.Order_Weight

The query is NOT returning the proper results.

For example, say the order consists of 3 Widgets:

3 x WidgetA (weighing 0.5 kg each)
2 x WidgetB (weighing 0.25 kg each)
1 x WidgetC (weight 0.25 kg)

What I would LIKE to see in my query result is
     od_totals.Product_Count = 6 (i.e. 3 + 2 + 1)
     od_totals.Order_Weight = 2.25 kg (i.e. (3x0.5kg) + (2x0.25kg) + (1x0.25kg)

I hope you're "with me" so far.

However, this is what the query is returning:
     od_totals.Product_Count = 3
     od_totals.Order_Weight = 1.0 kg

So what have I done wrong. Can somebody please help me redo the query to return the correct results?

Thanks guys!  :D