Thanks very much, folks, for your insight and input.

A couple of points:
- next day, I tried OLCI just for me and got the same message;
- in the past, I have had two IE browser windows open at the same time, to ensure we both had the same choice of seats, and didn't get this problem;
- I checked in the 'My bookings' area online and all details were correct.

OK, we can survive without OLCI, but it is such a useful device, we miss it when there is a glitch.