Error message: "Please correct the highlighted errors and try again."

Now here's a wonderful problem: I've written a stunningly brilliant message (OK, maybe just a stunned message), but when I try to post it, I get this error message: "Please correct the highlighted errors and try again."

 

The problem is, nothing is highlighted! I spell check it, and tell it to "learn" the wrong words. I try to post again, and now I'm accused of posting the same message more than once in an hour (3,600 seconds). But it TOLD me to "try again." So it's a double-gotcha!

 

See screen shot to illustrate what I mean. -- oops, I guess not. Another error message says that txt, log, and lue are the only valid extensions. Images out forbidden. Oh well, I think you get the idea.