I have no idea what happened - everything's checked on, both in options and individual user profiles, so it's definitely enabled, but for some reason it's off, though I've never touched the option before.
When my posts loaded before, there would be a brief pause as they switched from HTML over to RTF. Now they just load as HTML, and I get the "tinyMCE is undefined" error in the lower left portion of the browser status bar.
Any ideas? I've tried unchecking, updating, and re-checking and updating the RTF setting at the global and user levels to see if this would reset things. No dice.