Re: Buddypress 1.2.3 to 1.2.4 ugrade FAIL!
You must always deactivate any BuddyPress-specific plugins before upgrading or reinstalling BuddyPress. That is why your first attempt failed. Moving your plugins outside of the /plugins directory basically accomplished that for you.
From that Codex article:
“…it’s a good idea to disable other BuddyPress plugins first of all”
Since BP 1.2, all BP-dependent plugins should have code that will prevent them from firing if BP is not activated. However, some plugin devs have not added that coding to their plugin so you can have issues.