Installing a completely new Dynamics CRM 2011 on top of Windows Server 2008 R2 and a separate SQL Server 2008 R2 I faced the following issue:
Windows NT user or group 'MYDOMAIN\SQLAccessGroup' not found. Check the name again.
Everything was right (the account I was using had enough privileges, the group exists in the AD, etc.).
After some research I found some links that talked about the problem but didn’t match at all with my scenario (i.e. one talks about a german deployment issue). Then, I came up with this thread, where I found some (unbelievable) clue: it seemed the install process was not able to create the login in SQL Server because a SQL Server Management Studio query window was open and locked one of the system DB.
Odd, but true :p). But, just by closing SSMS was not enough.
In my case, I had a Remote Desktop Session opened with my SQL Server.
So, my solution was: just logoff SQL Server remote desktop session :p)
This way everything was closed.
Then, got back to my Dynamics CRM setup and clicked on “Retry”. Installation continued smoothly :)
Hope it helps to save somebody else’s time.
PP [twitter: @pabloperalta]