Windows 7 - VNC cant access a machine after it has been acessed via Remote Desktop

Hi,

I use both Remote Desktop and VNC. With windows XP I found that if I connected via RD then any subsequent attempt to access the same machine via VNC would connect BUT it would just show a black screen. Apparently this is some 'security feature' in RD and the workaround I was given was to disconnect the RD session by issuing the command:
TSCON 0 /DEST:console
After this VNC would have no problems connecting to the machine.
So, now I have moved to Windows 7 I am having a similar problem. If I connect with RD to the Windows 7 box then every subsequent attempt to connect via VNC the connection gets closed the second it connects with the msg:
'The connection closed unexpectedly, do you want to re-attempt ....'
When I try the same workaround I get the response:
TSCON 0 /DEST:console
Could not connect sessionID 0 to sessionname console, Error code 5
Error [5]:Access is denied.

So does anyone know is this the same problem with RD causing problems for VNC and if so is there a Windows 7 equivalent of the TSCON 0 /DEST:console command ?

Thanks,

Usjes.