I installed an Addon (CommentAuthorInfo) who didnt work, I dont know why. Just after installing it, created a topic, and when I clicked Submit, it leaded to a 404 error. So I created it again, and I made the same thing. I went back to the "discussions", and they both were there. But when I click one of them, it leads again to a 404 error. Help please :)
If you're sure it's because of CommentAuthorInfo, you should post there. Not 100% but it could be that: Open your conf/settings.php file, and check this item: $Configuration['BASE_URL'] = 'http://www.site.com/forum/';
Oh, I think i found out. Is there some kind of security with Vanilla ? Cause I made many tries, adding stuff by stuff on the discussion (new lines, then BBCode etc...) to see which extensions was not working, and finally it didnt worked when I added the word "pornography" (it's a topic for the forum's rules).