hi, I am having a similar issue. When I try to post a topic, as admin or otherwise, I get the same error – “There was an error posting that topic.”
It posts to the forum though, I can see it there, but it just does not show up on the buddypress front-end. I do have that line ($bb->bb_xmlrpc_allow_user_switching = true;) in bb-config.php
Any thoughts would be greatly appreciated. thanks.