If you’d like to help, head over to the miniBB homepage and see if you can find anything about this bug. I won’t have time to do any detailed searching myself until at least Monday.
Edit- I’ve found something that may be a clue. If you do a search on the forum, it will come up with a list of posts but all the titles will be n/a. This suggests to me that there’s some kind of database issue going on, although I know next to nothing about these things and could very easily be wrong. In any case I’ve backed up the blog.