Sorry it took me so long to get here. Real life (not the holiday; some medical problems in my family) kept me away from the forum for a few days.
When somebody posts something that the forum software can't handle, it refuses to display the page that thing is on. As you've discovered, you can keep adding messages after that happens until they roll over to a new page. Or you can go to Look And Layout in your Edit Profile pages and choose to display a smaller number of posts on each page, which will reveal more of the posts that were hidden on the broken page.
But please notify me whenever this problem occurs, because I'm currently the only one around who knows how to fix it.
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gonZo