This past week and a half I've been playing around with some bookings, and am actually seeing the reverse scenario (this is primarily domestic U.S. and South America segments on AA and LA). BA.com is showing availability and even takes me all the way to charging my card, but then after a minute or so, comes back with an error message that my request cannot be processed - please call BA service center.

When I then call BA, they are unable to see the availability that the website shows. Sometimes it's only one segment that differs, sometimes more. I've only called twice as the other times were after-hours.