I have seen this once before and never found a solution for it. I have just installed a fresh copy of unity 5.x on an MCS server with Server 2003 and Exch 2003. During the install process i never logged in with the unityadmin account.
Now that the intall is complete i logged out of the unityinstall account and attempted to log in using unityadmin. The server begins to log in, then just sits at a blank blue screen indefinately.
I tried creating a completely different user account and it does the same thing with that one.
The server is a domain controller in a voice mail only configuration. The unityadmin account is part of the domain admins security group. I have tried deleting the profile directory for that user, but it does the same thing the next time i try to log in.
Has anyone seen this problem? Does anyone know a solution? It seems like its some type of windows permissions problem, but im not sure where to look. There are no event logs showing a problem when the user attempts to log in.