Yeah, it's not just your imagination. If you try to post something and get a white screen, don't refresh the white page (doing this will resend the post) or try to post it again. That's what seems to be causing the multiple posts, so just leave it alone and whatever you posted will show up in a few minutes.

I'm no expert when it come to computer shenanigans, but I'd guess it's happening due to the server lagging or being overloaded, thus taking some time to catch up and actually show your post.