If you are using rewrite=slugs and mod_rewrite (not multiviews) there is a possibility for a user to ignore an entire topic that ends with a member they just ignored. The one time that happens, bbPress redirects them to /topic/ (ending in blank) which the default rewrite rules don't support. So the member will then get get some weird result like a 404 error page. To fix this, add something like RewriteRule ^topic/$ /forums/ [L,QSA] Where "forums" is the name of your bbpress root directory. Again, the multiviews and non-slugs setups should (in theory) not be affected.