I just received an email from Mturk telling me that a requester had blocked me from working in his HIT's. Now, I've done several hundreds of hits for him (easy ones...$0.05 each-they have been accepted and paid very quickly, always with a nice "thanks" note). I am puzzled! If someone blocks you I understand that it is due to a bad quality work, if so...isn't supposed that they should have rejected or not paid for your hits at all? And even a nice note thanking for each HIT? Or are there other reasons for blocking a turker? Thanks!
It's actually quite easy for a requester to block a worker by mistake. Considering your good past history, you should contact the requester and ask for an explanation and removal of the block.