Windows 2003 server R2, 64-bit, service-pack 2, running Active Directory.
Regardless of whatever install-combination-choise for "Protected application execution" and "Allow all users...", installation always fails with a "Failed to add user to the 'boinc_admins' group (Administrator).", or "Failed to create the 'boinc_master' account".
This is on a new installation, that has only had BOINC v5.10.45 before, and trying to install as Administrator, so it's not a case of lack of privileges...
Earlier v6-clients has similar error-messages then tries to install.
I did do a test of v6.2.1 on a non-DC win2003, and in this instance installation didn't give any problems. But, it's unlikely anyone will de-promote their Domain controller just to install BOINC...
This atleast means, if anyone else tries to replicate the problem, it's a waste of time to try it on a windows-server that isn't running Active Directory...