<p>I just found <a href="http://meta.stackexchange.com/questions/99141/bogus-you-have-already-voted-to-close-this-question-on-expired-votes">this on mSO</a>. To quote Jeff's answer</p>

<blockquote>
  <p>This is correct. You are only allowed to cast one close or reopen vote
  on any given post, largely to prevent close/reopen wars involving the
  same cast of characters.</p>
</blockquote>