I up-voted a question. My up-vote got marked. I also up-voted one of the comments on the question. Then I accidentally closed the window. Using Google Chrome's Ctrl+Shift+T, I reopened the closed window. I noticed that my votes were missing. I up-voted the question again. It got marked. It said "You voted on this question 6 minutes ago. Your vote is locked until the question is edited." I knew something was wrong.
I reloaded the page. The up-votes on both the question and the comment were visible. However, my up-vote on the question was locked.
I assume this is a bug. If not, please let me know.