Update and subquery

[DenBurt]

I have created a query and I recieve an error stating that the operation must use an updatable query. The query I am trying to update is updatable and is very basic I only want to update a price field. The query to update is merely a mirror of the underlying table itself. The Price I want to set it to is a list from a subquery. I created a query (contains all price changes for 1 month then averages them) I base my subquery on this.

My update SQL is as follows:
UPDATE SwingSwap1 SET SwingSwap1.AvgPrice = (SELECT LocalUpdateGD.PRICE FROM LocalUpdateGD Where LocalUpdateGD.[DDATE]=SwingSwap1.DeliveryMonth);

I have even tried:
UPDATE SwingSwap1, LocalUpdateGD SET SwingSwap1.AvgPrice = [LocalUpdateGD].[PRICE]
WHERE (([SwingSwap1].[DeliveryMonth]=[LocalUpdateGD].[DDate]));

If anyone can help it would be appreciated. Thanks in advance.
Dennis