I have to click Preview first, then post from there. First time I realised this was just after I'd written a massive post, so was very glad I could click Back and try again.
Incidentally, ridiculous amount of white space in the post box. I can start a post anywhere in the box, and sometimes a space appears about 3 inches wide until the end of the line- a bit like when you're typing text with both line ends justified, if that makes sense.