Unable to delete a DC - dcpromo error

Deleting a DC is most of the time a rather straightforward procedure but a few weeks ago i received the error message below trying to uninstall a customers DC.

"The operation failed because: the attempt at remote directory server serverx.customerdomain.local to remove directory server CN=ServerX,CN=Servers,CN=customerdomain,CN=Sites,CN=Configuration...
was unsuccessful. "Access is denied"

The account which i was running dcpromo with was both Domain Admin and Enterprise Admin, i could ping the other DC's, i checked with ADSI edit that my account had the rights to delete the DC. Everything seemed ok.

So what was the problem? I had a look in Sites and Services and found the solution to my problem. The DC had the checkbox "Protect object from accidental deletion" ticked. I unchecked the tickbox and could then run the dcpromo without any problems.