No one has reported that issue before is there an error in your dnn event viewer?
-Scott
Have you manipulated the data in the tables outside of the cart using sql server? Or have you made any customizations to the ascx pages?
That probably has something to do with it. When you imported your data did you check the checkbox in the sql server import wizard to allow identity inserts? Most likely what has happened is the primary keys on the product table or child tables are out of sync.
Yes it should here is the stored proc for deleting a product its pretty simple. Does it exist in your sql database?
ALTER PROCEDURE [dbo].[dnn_Smith_DeleteProducts] @ProductID int AS DELETE FROM dnn_Smith_Products WHERE [ProductID] = @ProductID
Ya this is definitely a wierd one. Maybe its a permissions issue or something in your database does the sql account in your web config have the proper permission to delete records? Try checking your sql server logs and windows event viewer logs.