You thought the maintenance period would fix it?
*Chuckles haughtily.* Maintenance periods never result in anything. They're just Web Presence having a laugh. 'Make them think we're doing something!' they bellow across the tumbledown, cubicle strewn wasteland that is their office.
But yeah, I've been having similar problems. I sometimes get that screen when I post a message (though thankfully not very often), and occasionally a page just won't load. No error message, no random images scattered confusingly around the page, but nothing. A refresh fixes it.
Just make sure you copy the contents of the posting box before you submit a post. If something goes wrong and you need to go back, it's quite probable that it will delete the contents or lock the box so you can't do anything to it. Everything about this forum screams 'my first JSP project'.

Except, of course, the bits that were programmed by the original developers before SOE figured it'd be a fun idea to copy it and
ruin it for their own site.
*Makes a very loud noise expressing frustration.*