I made it work for me, hope it works also for you all.
Go to Settings – Forum and select the “auto role” box ( Automatically assign default role to new, registered users upon visiting the site.)
After selecting this box in my website everything works fine.
Hello. I have the same problem, forum works if it’s open,but in private modus a 404 page ( even the “admin”account).
I can see the private forums when logged in as a user ( or admin) but clicking it gives a 404 page
Using Worpress 3.4.2
using bbpres 2.2.1 new install
Registration at website by registerform from the Formidablepro-plugin