I am having the same problem. It seems it is a permalink problem. In my buddypress/pages, the pages that doesn´t work is “discussion forum” ( I only use site-wide forum ) and page “register”. Alle the other pages work fine. The pages are created in the same way, but the two that doesn´t work link back to my home page all the time.
I have changed the name in the “Settings > Forums” in wp-admin; where there’s an text box option that defaults to ‘forums’ but I still have the same problem…I have deleted the BP plugin, reinstalled and tried again, but no luck.
If someone could just make a step by step tutorial to how this is done in the right way, or maybe it exists already…I would be happy to see it