I've made no changes to the site, database, plugins, theme or anything over the past week or so. However, every post I've had scheduled for today has "Missed schedule" in the reading. Even if I reschedule them for one or two minutes in the future, the problem returns. I can, however, manually push them live by setting their time to something that has already past.
Any idea why this would all of a sudden be an issue? I typically schedule 3-5 posts each day, and this has never happened before.