It really is all about the "Back" button. Hit it, and like an errant schoolchild, you are sent to the back of the room. The site appears to be loaded with cookies, so the cache takes over, and just keeps telling you that you can''t complete the booking. Conventional wisdom says, "don''t hit the back button", but with such complex, date and time sensitive fares, which appear to change by the minute, it is virtually impossible not to have to look at alternatives. In the NYC area alone, you are talking 3 to 6 airport options, depending on how aggressive you feel about finding the lowest fare.