It's good they're paying it.
They left me a voicemail message this morning to say they'd issue a correction and pay a dividend but I was in meetings and just got it.
I would like to think it's just a mistake although they should be more professional than to put out a notice to advise they won't pay people in error. Still I hope that's what happened and that they didn't back down due to "constructive feedback" as I don't like to deal with companies that only do the right thing when pressured.
So now I have to decide whether to invest or not. Thanks all for the replies.