Is the seller Not A Registered User (NARU)? This means he has been removed from eBay for being naughty.
Usually this is pretty serious, counterfeit items or fraudulent dealings, but occasionally a seller forgets to pay his eBay fees and gets caught up in a NARU.
Allow the 20 days for the item to arrive, unless the seller's feedback is ugly (anything under 97% positive is bad). Then open the Item Not Received dispute and get your money back.