If you change any thing on the message part you will not get the duplicate submission message. ( Well, that is how it should work) It could be as small a putting a space some place or and extra dot at the end of a line.. Just changing the title will not do it.. This it part of the bbs system that is to try to help duplicate post by hitting the submit button twice on a slow system. It does have a problem in that area, I think a preview should not fall into that area but is seems too. ..
Dr.D