I had a similar problem with a redemption booking last week. I had been checking it occasionally to make sure seats or times hadn't been changed. When I went to check in at T-24, I could get as far as the confirmation that I had no knives or knuckledusters and then it told me there was a problem and I could not check in.

Called the EC and they said they could see there was a problem but could not diagnose it. Had to check in at the airport. After that, the booking completely disappeared from ba.com even though there was a return leg. Checked in for the return at the desk at it was all good.