IE is not the first pick I would choose though. Nonetheless, I don't believe this is a browser related issue, I've encountered it a couple of time before. It is the same type of issue when you for example overpid the Opening Poster and your reply ends up above the OP (If you've ever seen this), it all has to do with the connection between server and client I believe.
It can happen if there is a communications error with the AJAX submit and the normal submissions occurs at the same time. There is code that tries to prevent it but it isn't 100% foolproof, I'm sure V has implemented it. Unfortunately, you have no control over the communications between the client and server. You can't really do anything about it alone.
I'm not sure though. ^