I couldn't find an existing post which surprises me considering this has been around for a while.
Very easy to reproduce: go into the flag queue and perform the 5th closevote.
This causes the 'Vote to close' button to infinitely 'load' (the window never dissapears) and the little closing icon (which seems to be part of a window) to appear. The latter can only be closed manually, it doesn't dissapear by itself.
This happens on both my laptop and my desktop using Chrome 33.0.1750.117 m and 33.0.1750.146 m.
Operating systems are Windows 8 and Windows 8.1.
After closing the (bugged out) window, the underlying "close" button is still visible and has "close question (4)" as display text even though 5 votes have been cast. Clicking it again results in the popup saying the question has been closed.
This is a question with 5 votes on it.