This isn't a bug - it's a security feature.
Yes, the behavior does seem a little wrong, but it's as designed. Here's the story.
In the early days of the UBB, the topics were stored as .html files. You could easily find a topic by looking for a numbered .html directory in a forum directory, i.e. NonCGI/Forum1/HTML/000000.html
When it came time to implement private forums, this feature became a liability - anyone could easily explore any forum directory and find topics.
The solution was to store the topic data files and topic .html files in different directories. So, when you switch the forum from one mode to another, the actual place that the data is stored changes, which is why the topics seem to disappear and reappear.
In the 6-series, all requests go through the scripts, so technically, the different private fourm directories are no longer required. However, we've held off on changing the behavior because of a number of other potential quirks... for instance, what would happen if a forum contained topics in both private and public mode, and the two were merged? Would the current mode take over, completely destroying the topics in the other mode? Would they be merged?
Anyway... For now, the solution is to use the Move Topics tool to move all the topics from your private forum to a new public forum. You should then probably delete the old private forum completely.
(Previously I've advised just making the old private forum public, then moving the topics back in, however this will result in worse bookmark breakage. If the forum is deleted, the user gets an error. If the topics are rearranged, the user will get a completely different topic instead. That's probably worse. <img src="https://www.ubbcentral.com/boards/images/graemlins/smile.gif" alt="" /> )
If you don't see a Move Topics tool under the Maintenance menu in your control panel, you'll need to upgrade to the latest release.
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Charles Capps
UBB.classic™ Developer
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