Yahoo! has updated their checkout system and the final updates went into effect 01/22/2009.  If your customers see the following message when they place an order, you need to update your add-to-cart form.

Error: order.store.yahoo.com is not a valid URL. Please point all checkout actions to order.store.yahoo.net

You have encountered a file path that is no longer valid. Please contact the store merchant to continue with your order and to report this error.

You either need to update the view cart form or more likely the add-to-cart form so it points to the .net domain.  This change is required when switching to catalog manager.  With Yahoo-built forms the urls change automatically but if you have hard coded urls in the templates or html, those need to be changed manually.

Your Store Wizards can help.  We will find and update the custom rtml/html which generates the view cart or add-to-cart form.