I can't seem to be able to have multiple administrators connect to Windows Server 2008 R2 Standard. Each time a different administrator logs in, it takes the current session away from the user and gives it to them and boots the original user from the server.
I've also tried connecting 1 instance normally and a 2nd with the /admin flag on remote desktop and that didn't matter either.
It is not about administrative sessions, it is about the user. Unless you reconfigure it the new default is only one session PER USER.
There was an issue with the old approah that sometimes the server would not recognize it is a reconnect so an admin would run out of sessions.
I suggest you just dont run multiple conections - ON ONE ACCOUNT. Create separate accounts per administrator, as is best practice anyway.
Without any RDS licensing, Windows Server 2008 R2 allows for two concurrent connections for management from two different users. If you have two users sharing an administrative account, when one logs in he will "hijack" the open session of the other admin unless he explicitly connects to a new session, which is not the default RDP behavior.
Shared accounts are a audit nightmare and security risk. That being said.. If you must use the same account for multiple users
Check the Group Policy for "Restrict each user to a single session setting"
Changes to remote administration in Windows Server 2008