If I login to a particular instance of SQL Server 2008 using a Windows domain user who is in the sysadmin
role and I create a brand new database via SQL Management Studio, a user in the newly create database is automatically mapped explicitly for my local MACHINE\Administrator
account.
This doesn't happen on any other SQL instance I have running, or for any other user on the problematic instance. I'm thinking there must be a setting somewhere (at the server level or the user level), but I can't seem to find info anywhere in Microsoft's documentation or on the Google.