logged into a vista domain member as administrator, when I go to the 'member of' tab in dsa.msc for a user account other than administrator, and click on 'add', mmc crashes. Didn't try manipulating group membership of the administrator account.
This seems to be vista specific. On my Win2000 environment it works.
Please retry this one! If the problem remains, try to provide us more information: logs, wireshark captures...
This is going to be closed, because no further information was provided. If the problem persists, please reopen!