A couple of minutes ago, the front page of the main site showed all the normal header and sidebar stuff, but no questions. I refreshed and re-opened the page several times, and it didn't help.
The problem went away on its own. The problem doesn't appear to have lasted more than a few minutes.
As of Sat 2013-02-09 02:25:55 UTC, I'm seeing the problem again -- and it just went away again.