Given the “imminent” demise of Windows 7 – this was an interesting one which may well be Windows 7 specific. A client had been accessing a desktop PC via RDP across a VPN when they reported a error. The dialogue read “Your computer could not connect to another console session because you already have a console session in progress”.
When checked of course the user does not have a session open. Checking the IP address that they are connecting to against the actual IP of the machine itself shows a discrepancy – they are not the same !
After some digging it appeared the IP address of two machines had been swapped and another user happened to be connected to the machine at the address this user was endeavouring to control ! The names of the machines had not changed with the swap of IP address but both users were using an IP address not a machine name
It struck me that the error message should really have read – “The certificate I have stored for this remote machine doesn’t match what it thinks it is – and by the way there is a user already controlling it !!”
Correcting the IP address to be the dns name of the machine to reach the correct machine allowed the user to control it – AFTER accepting the certificate messages you get when connecting to the PC in this manner.
If the address of the machine changes – the certificate you previously accepted is no longer valid !
So the moral of this one is – make sure what you think you are connecting to is actually what it is !!