This morning we called the support number the British Airways error message instructed us to call, hoping to find out whether our reservation had gone through. The first thing we got was a message instructing us to go to their website, since we could make reservations there (um, hello, we're calling you because your website FAILED), and then the recorded voice nicely told us that any booking made through their internet support service would be subject to an additional $10 fee per person.
At that point we hung up.
We checked our credit card company, who confirmed that no charge had been made, so we decided to try the British Airways website again, hoping the problem was transient. We got the same error message.
We called British Airways' support line again. We got the same message to go to their website. We got the same notice about $10 charges. And we got put on hold.
Finally an agent talked to us, and asked if we had checked the box indicating that one of the passengers is a US citizen. We had, and the gentleman said that it had probably brought up a screen asking for emergency contact information. The website had, and we had added all the contact information requested.
The service rep then said that what we needed to do was make the reservation again, but not check the US citizen box, which would then not bring up the contact information page, which would then let us make the reservation without an error message.
We went back to the site, didn't check the citizen box (meaning that we didn't put in any emergency contact information), but did everything else the same, and this time the reservation went through.
I asked the representative how long this problem had been occurring; he responded, "Since we put that feature onto the website. We get many calls about it every day." He didn't directly answer my followup question about how long the problem had been around, but implied it had been at least weeks.
So, British Airways has a known problem with their website that gives customers a useless error message leaving customers unsure whether their thousand- (or more) dollar purchase has gone through (and that does, in fact, prevent the purchase from going through), they don't have tech support online at night, and they've known about this issue for weeks, yet they haven't fixed it.