GOOD LORD this is frustrating!
Same shite is happening to me right now.
I waited so long for my reply to be posted, I just copied it (y'know, for when it was gonna get lost) and hit refresh, and was told a new reply had been added....IT WAS MINE!
Came here to tell you about it, posted a reply in this very thread, got an error message about "you've already posted this", which I HADN'T, and I most definitely HADN'T double-clicked my mouse either.
GAH!