It would be nice not to lock a vote for first hour or so because it is quite common one can make a mistake and want to reverse their vote. Or, at least the original poster is nice enough to comment on this question to clarify it. It happened twice to me today after 10+ months as a member here. I never came across it and I thought is this a new feature?
The real problem is explained in the question Undo an up/down vote after a comment is left
I downvoted the following question because I thought it was a very basic question and I commented to OP, "did you do research before posting this?". The OP relied "yes". Then I dug a little and could not find a clear answer myself. So I answered his question. Later, I tried to remove my downvote but I could not.
On the second occasion, I upvoted an answer but realized later on that the answer did not quite work for me. The way I got foiled was the top voted answer was not voted as the accepted answer which was a better solution. After read the OP's comment thats it worked, I implemented it and it was the right solution. Now I wanted to undo my upvote on second best answer but I could not. It is highly unlikely that the answer I want to remove my upvote from will be edited because it is an older post, and secondly SO advices not to edit your answer unless absolutely necessary. I should be able to take back my upvote just to help other visitors, the right question is upvoted. Here is that screenshot:
Is it possible that user are allowed to reverse their up/down vote for 1 hour after they have voted?
By the way, I could reverse my up/down vote before, I dont know what happened or maybe I just never came across it.