This explains how to solve a problem if you logged in to the domain, via your computer, as a regular user, and then you need to run Active Directory with Administrator privileges as another user.
First open CMD.exe as Administrator.
C:\WINDOWS\system32>runas /netonly /user:mydomain\carles.adm "mmc.exe dsa.msc /server=myserver.mydomain.com"
Assuming my regular user is: carles
And my Administrator user is: carles.adm