BuddyPress.org

I switched to the BuddyPress default themes… still failed with the media library duplicate, but I can add friends

Well, one problem isolated. So, this particular issue appears to be caused by your custom theme. Make sure that you compare the header file in the bpmember theme, or even the bpskeltonmember theme, with your custom header file. You could be missing a key line or two.

Concerning the duplicate declaration error: were you running an older version of BP before–like RC1? If so, did you delete all your old BuddyPress files from /mu-plugins/, this includes theme files.