Why am I increasingly getting a "We are experiencing some problems, please try again." message when trying to submit an answer?

This seems to happen even when other users are still able to submit answers. It's really annoying.
Update: Thanks for the answers so far but if the user has blocked me shouldn't the answer box be absent so I don't waste time typing an answer? That has previously been my experience. Also, could an anonymous user block me which was the case the last time this happened?
Update 2: Thanks for that answer Dragos Drakkar. Crazy isn't it? Just another of the joys of using YA!
Update 3: I guess the I shall have to type a single character in the answer box and click 'submit' if the asker is anonymous and then edit the answer if it is accepted.
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