From time to time I get a message saying...
'Sorry! You have already sent this message. You may have refreshed, or clicked post twice!'
This happens on the first time I post, and it's not legitimate (that is to say, not a real error). It's (thankfully) a minor problem, as I can simply go back and copy what I wrote, post again, wait 30 seconds and then paste and post, but it does get a bit annoying. It seems to happen with my longer posts, as well. It also happened with one of my messages...
Like I said, nothing too big, just a little cosmetic blip.