so i just tested this in elgg 2.1 and found that after i enabled the option in the group plugin to allow non admins to create groups and then signed in 'as' a non admin, then clicked to create a group - i am told that only admins can view that page.
So in Groups you set "Who can create new groups?" to "Logged in users" and in Group Tools "Site administrators need to approve new groups" to "Yes"?
I tried this on my test site and didn't get the error message. And the normal user could create the group
so i just found that if i disable group_tools latest version and my site's theme and any plugins i know of that interact with groups, then non admins can create new groups. but if i enable group_tools, then non admins are unable to view the group creation page. i don't know any more than that presently.