All of a sudden the server name would be the default to log into instead of the domain name. This was frustrating our users, who were used to logging in just with their username and password, they never worried about the log on to box. So I found this fix after some research.

1. Open regedit

2. Navigate to My Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon

Change the key DefaultDomainName to your default domain, and that’s it. Try logging in now.