Garry Martin alerted me to a useful piece of information this morning…
It seems that the /console switch introduced to the Remote Desktop Connection client in Windows Server 2003 has been deprecated in Windows Server 2008 (and Windows Vista SP1). It fails silently (so you still think that you are connected to the console session) but closer inspection reveals that a different session number is in use.
The replacement command is
mstsc /v:servername /admin – John Howard has more information on his blog.