This is happening to me to. I get around it be clicking "preview" instead of "post" first. You still get the "fill in title/text" message, but if you return to the previous page and click "preview" again, then your message comes up and you can click "post" then.
It's a pain in the ass doing it this way, but it'll work (you still can't italicize, bold, etc. or add links using the icons, though, and attempts to edit posts seem to fail half the time).