When you say populated, do you mean invited or have you logged in as those users and joined the groups (or accepted the invitations)?
The latter. I logged in as the test user and then joined to group. When I check group membership it shows the correct number or users in the group but when I click on membership it displays “this group has no members”.
I wanted users to be able to join groups on their own and then once they have joined to see the other members of the group. Is this not possible?
No, it should be possible, that’s sort of the whole point. 
I assume these are public groups? Are you running WP or WPMU?
I get the same behavior in both WordPress standard and MU on my test server. Yes they are public groups.
Any ideas here? I must be missing a setting somewhere, no?
Sorry Jim, I tried the same on my WP 2.9.2 + BP 1.2.3 install and I can’t reproduce the problem you are seeing.
I’m seeking an answer to this issue, too. In fact, that bug is actually existing right here. Click on “members” at the top, and you get “this group has no members.” (For my blog, it just keeps me in the home page of the group. I can’t see a listing of group members.)
Help?
OK, I found a workaround. I replaced the string ‘members’ to something else, like ‘students’ in files within the bp-themes and bp-groups folders. Works like a charm, now.
I am having the same problem with WP 2.9.2 + BP 1.2.3.
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.
