It's done that to me too. It has another one that says something like "you already posted that" ---- no I didn't!
I'm not exactly sure what it is all about. I suspect that it is in there to help prevent spam stuff. Only maybe it goes stupid once in a while. Considering all of the spam stuff I am perpetually deleting, I suspect that this may be one of those things where the upsides outweigh the downsides.