BuddyPress.org

No, BuddyPress works with MU. I have it working fine on an MU site. WPMU 2.9.2 and BP 1.2.3.

I see there are a few other posts with similar issues

https://buddypress.org/forums/topic/404-error-on-bp-links-1

https://buddypress.org/forums/topic/404-error-on-buddypress-links

These are for IIS – I’m not on IIS, I’m on Apache

https://buddypress.org/forums/topic/404-error-on-bp-links

https://buddypress.org/forums/topic/buddypress-menus-give-404s

I’m going to scrub my DB and try again.