Trouble shadowing remote RDP sessions on Server 2008

http://support.microsoft.com/kb/976110

Shadow attempts yield Error "the requested session denied remote control". This can occur when using RDC less than version 7.0 against Vista or Windows 2008. There is a hotfix, or there are workarounds on either client or server.

Server-side workaround, launch gpedit.msc, and drill down to
Computer Configuration\Administrative Templates\Windows Component
.. and on Windows 2008, expand
Terminal Services\Terminal Server\Remote Session Environment
... or on Windows 2008 R2, expand
Remote Desktop Services\Remote Desktop Session Host\Remote Session Environment
.. and then set the value "Set compression algorithm for RDP data".

The article says set it to "Do not use an RDP compression algorithm", but I set it to "Optimized to use less memory", and that also worked.