We'll have to temporarily take the forums down as the search index rebuilds itself then if you want that
Apparently the limits are between 3 and 15 characters in the CP though, so I don't know what gives, other than taking the forums down to rebuild the search index from scratch
Although I think temporarily closing the place is just to be on the safe side, I can't see it being a huge problem if the index rebuilds while it's still open
