I’m seeing the same issue with WP 3.8 and bbPress 2.5.1 when MemberDeck 1.2.1 is activated. I reached out to their developer and with debugging turned on the following error occurs with the bbp_setup_current_user function/hook:
The current user is being initialized without using $wp->init()
I see a ticket for this already filed with both bbPress and upstream in WordPress:
https://bbpress.trac.wordpress.org/ticket/2412
https://core.trac.wordpress.org/ticket/24169
