As of late, we are experiencing this business of double posts. I suspect the reason for this is because after we respond to a thread, instead of our reply being posted, we are prompted by something like:

An error has occurred

or

Please wait 30 seconds before posting...

So we continue to try to post our reply to the thread; sometimes again and again, ergo the Double Posts.

Well, what I have discovered is that upon receiving one of these messages, I cursor to the top of the screen, to the selection "Whats New" and select that. In every case, my post HAS gone through... I don't 'listen' to the unnecessary prompt to wait 30 seconds....

Works every time. So no more double posts for me.

Very annoying, but a glitch in the system, je suppose.

Hope that this helps, even if it really doesn't make sense.
~K♥zzo