Still no update from SQ on this... except to say that they are working on it. I think that may actually be true, because whereas my miles balance still used to update after each trip (even though PPS value didn't), I haven't been credited with any of the miles or PPS value for my last trip that finished on 19 February. So I'm assuming they changed something about my account and it had the wrong effect. If I wanted an indifferent loyalty program I could have gone with Qantas instead!