i think i remember, that here in the forum are a lot of threads that says:
WP 2.7 + bbPress 0.xx = Nope!
WP < 2.7 +bbPress 0,xx = yes
WP 2.7 + bbpress 1.0 = yes
So, either you downgrade your WP or you use the alpha version of BBpress.
You shouldn’T get issues with login then…