This issue affected Stack Exchange as a whole.  **It has been fixed** for several minutes now.

More information is available in these Meta questions:

 - [I can post questions, but they don't show up on the front page or anywhere else][1]
 - [Is my question (incorrectly) banned due to fighting with spam?][2]


  [1]: https://meta.superuser.com/q/5576/83694
  [2]: http://meta.stackexchange.com/q/147246/188803