I've seen this many times over the past few months, on different routes (SFO-BOS or SFO-JFK). When I view the seat map, the single seats in row 2 show as available. When I book the flight, and get to the select seat phase of the checkout flow, row 2 is not available. They still show on the seat map as free. Has anyone seen this, and had luck actually getting those seats if they are truly available?