Replication Procedure:
Server Configuration: Win2008R2 with Remote desktop service role installed and Desktop Experience Feature installed. DPI changed to 125% or 150% in the Display settings edited on the console session.
Client Configuration: RDS 7 or RDS 7.1 installed and more than one monitor installed and configured with “ Extend my Windows desktop onto this monitor”.
Procedure: Connect to the server via mstsc with “Use all my monitor for the remote session” enabled in the tab Display of the Remote desktop connection client.
Issue: the session will hang ad infinitum on “Preparing your desktop”, in fact the desktop and the taskbar are created but the rdp client window does not repaint itself anymore. When disconnecting and then reconnect to the disconnected session, the issue disappears.
If changing back the DPI setting of the server to 100%(default) the problem disappears. This behavior was recreated on XP SP3 and Win7 SP1 and on virtual and physical 2008R2 server.
I hope you will succesfuly recreate the bug and send its description to the devellopement team...
Regards...