Error when posting to forum: "Correct the highlighted errors..."

The last few times I've tried to post a new message or reply to someone, I get the error "Correct the highlighted errors and try again", and below the editor box it'll say something like "The message body contains }, which is not permitted in this community.  Please remove this content before sending your post".  This seems to happen for random, innocuous bits of punctuation, and sometimes for characters that aren't even there.  I've tried it in the latest versions of Firefox and Chrome.  Anyone know if there's a workaround or fix for this?
 
By the way, I tried to provide a screenshot, but when I do it gives me the error "The message body contains 18 -02 -27, which is not permitted in this community. Please remove this content before sending your post."