BuddyPress.org

I have just had the same problem but followed the workaround listed in the thread above which worked.

If you can’t post in the forums:

1. Log out.

2. Come back to the forums, select the forum you want to post in.

3. Scroll to the bottom of the page, and hit the “Log In” link.

4. Log in.

5. You should be able to post.