This just occurred to me that I may not have mentioned it before. When a new member starts their first few posts they must be manually approved by a Moderator. This process is designed to stop Spammers. Anyway once the post/thread is approved it goes public. However, if the author goes back 5 mins later and edits this post/thread. It will be sent back to the approval queue and disappear from public view until approved again. Some new members will edit their original post dozens of times. Resulting in the post/thread appearing and disappearing multiple times. Normally this is not a problem. But for a special few.
Hope that helps to further clarify what the heck is going on!