Right now, due to the overload on the Stardock forums, people are ending up posting messages more than once. This problem has been addressed in generic forum software, but not here because the software is customized. The problem exists because receiving posts is a lot quicker than returning pages to the user, due to the bandwidth-intensive nature of outgoing pages, especially ones with high graphical content.
Why not create a page in-between the "submit" page and the return to the forum, which would be very low-bandwidth, acknowledge the receipt of the post, provide options to review your post/return to thread/return to thread list, and have an auto-forward after a few seconds if the user doesn't click anything which would send you to the thread list?
Seriously, this would virtually eliminate multiple-posting and would not be particularly hard to implement.