It appears that the database driving the forum software is having a few problems with its tracking of sessions.

If you are currently browsing as a guest, be that as a new user, or a registered one, do not try and login at present.

If you do try and login you will most likely be presented by a blank page, and any subsequent visits to pages on this forum will cause the same thing to happen.
If this happens to you, you need to delete the session_id cookie for forum.folding-community.org, the name of the cookie is phpbb2fah_sid, then restart your browser to make sure.

As long as you remain as a guest user, you will still be able to browse the forums, and you can track the progress of this problem in this thread: http://forum.folding-community.org/viewtopic.php?t=20820

Users who have set their profile to "Remember me" should not be affected by this problem and can post as normal.
It might be useful if members who can see this post, repost it in their home forums, just to let people know whats going on.