It seemed unusually quiet, and I just finally figured out why. The site logs on the database had grown out of control again (this has happened before), and so the database ran out of room. The net result would be that although the site itself loads fine, no new posts would be able to be added to the database. I apologize for the inconvenience, I have truncated the runaway tables and all is well again.
"Sadly then I knew the answer. All her life she was a dancer, but no one ever played the song she knew." - The Residents