BBpress has post permission error whenever you post some post and it doesn't let you create new topics or reply (make comments). The issue is because of the nonce used in the bbpress.
Resolution: You can avoid this bug by rolling the plugin to previous version which doesn't have this issue. e.g. BBpress 2.3 has error of posting but you can clear this by rolling out to the BBpress 2.2.4.
This is not permanent solution for this error but atleast you''ll be able to post in the forums. There doesn't seem to be official solution to this problem, or atleast not solved in forums as far as I know.
