BuddyPress suddenly fails to recognize admins and members

For reasons unknown, my BuddyPress Groups no longer have admins or, in some cases, members -- according to the frontend of the site.

(Note: this is a multisite with BuddyPress configured with the "root blog" constant.)

On the backend, all the member connections still exist.

For example, this group:

http://beta.nrocnetwork.org/community/groups/nroc-member-groups/university-of-okoboji/members/

You can see that there are two members in the group, but in the left nav, it says 0 members. And the user "NROC" is listed as the admin for this group on the backend, but as you can see, it says No Admins on the cover photo, where the admin's avatar should be.

We just noticed this problem a few minutes ago. Recent activity:

- Earlier today, one of our staff was associating existing users with groups and making them the admin. She was testing each one, and didn't notice anything unusual at the time. However, she may have overlooked it, as she was mainly working in the admin interface.

- I enabled, then immediately disabled, Floating Social.

- I updated one plugin (Super Socializer) that I haven't used in a long time, and activated it in the same site as BuddyPress. It seemed to work until I tried to save its icon settings. Then I got a 500 error. I immediately disabled the plugin by renaming it, and everything was back to normal. I wouldn't expect that plugin to have any connection with BP Groups.

Any idea where to start? Maybe disable and reenable BuddyPress, or the groups component? I might start poking around....but any advice would be greatly appreciated, as I'm at a loss right now.

P.S. Support access is open.