Error 1500 Windows cannot log you on because your profile cannot be loaded. Check that you are connected to the network, and that your network is functioning correctly.
on server 2008 R2 when trying to log in as domain administrator
Domain administrator entry in registry was missing.
This is how I fixed it:
Log in to another server,
go to HKEY_LOCAL_MACHINE \ Software \ Microsoft \Windwos NT \ Current Version\ Profile list
right click on key that belongs to domain administrator and export
move file to the server that expierience the problem (error 1500)
login to that server with different user name (local administrator)
import registry key
log in as domain administrator - problem fixed.