page404 after product was removed from shoppingcart as it has since been changed

problem: I log into my page (which is currently password protected due construction), then I see the message: “Product x was removed from the shopping cart as it has since been changed. You can add it back to your shopping cart here.” when I click on “here” (link), the 404-(error)page appears. how can I handle this issue? the message appears everytime I go on my page. thank you