Fix for multisite login bug in bp-disable-activation plugin

To fix the bug with multisite not logging in on registration, add this line after the password gets reset and before the auto-login code:

clean_user_cache( $signup['user_id'] );

It took me a while to track this down; the issue, for the curious, is that while the password does get changed after user creation, the cache of it isn’t getting invalidated, therefore the password fragment (which is used in cookie creation) is different, and therefore the hashes for the cookie don’t match what is expected, hence, no login.

Hope this helps someone else; cheers.

http://wordpress.org/extend/plugins/bp-disable-activation/