It is truly a buyers market. If you are getting disturbed by this one buyer then I assume you are not getting much interest. Your price is simply too high for sure nuff buyers to get excited about. Cut the price by a meaningful amount(10 to 15%) and see what happens. If you are underwater then consider strategic default. Be sure to get a legitimate chain of ownership if you are foreclosed on. If no one can establish legal ownership then you cannot be foreclosed upon.
Much lower prices dead ahead as debt ridden America resets to mark-to-market instead of mark to make believe accounting.