Looks like you might be running into CSCsg42469.
Here is the Release-Note:
Symptom:
When a new user (domain/locale) is created, provided administrator rights and used to log into the windows 2003 server console, the login hangs at a grey blank screen. It appears that the login is made however the desktop and task bar (start menu) do not appear.
Conditions:
Unity 4.2.1
Windows 2003
Workaround:
When logged in with administrator stop Unity services, then login with new user account. The login will complete. Then use the new user to start Unity services, then that user will not have any problem logging in on console or RDP from then on.
Further problem description:
Steps to recreate:
- Install a vanilla windows 2003 Unity 4.2.1 implementation
- Create a new user and give them domain admin rights
- Log off and log on as new user
ISSUE WILL OCCUR: GREY BLANK SCREEN
- press ctrl-alt-dlt to log off
- log back in as Administrator
- Stop Unity services (task bar)
- Log back in as new user
LOGON WILL FUNCTION CORRECTLY
- Start Unity services
NOW THIS USER WILL ALWAYS BE ABLE TO LOGON
NOTE: If you do not start Unity services with that user and log off, log back in as Administrator, start Unity, log off and log back in as new user the issue reoccurs. So it appears that the issue is tied to Unity services.