BuddyPress.org

I was also having this problem in clean installs of WP 2.9.2 + BP 1.2.3. I finally tracked the cause down to this: https://trac.buddypress.org/changeset/2882/trunk. Basically there’s a defect in the script that inserts the initial row into the xprofile fields table (wp_bp_xprofile_fields). A workaround (if you have SQL access) is to run these 2 statements:

ALTER TABLE wp_bp_xprofile_fields modify order_by varchar(15) not null default ”;
INSERT INTO wp_bp_xprofile_fields (id, group_id, parent_id, type, name, description, is_required, can_delete)
VALUES (1, 1, 0, ‘textbox’, ‘Name’, ”, 1, 0);

After I executed those statements, it shows my group members.
Note that the changeset also added a default for order_by, so I’m guessing that caused problems as well.