Hyper-v does not shut down pc

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http://serverfault.com – I log in to my Hyper-v host server I open the Hyper-V manager, select my server S1 and click Connect When I want to shut down server S1 or reboot server S1, I just click the start button and select shut down or restart (it's a server 2008 r2). Now this is my problem. The Connect window turns blue (like the default background of the server) and doesn't do a thing (not even after 10minutes, I also don't see any cpu activity in the hyper-v manager). Only when I select "Shut down" in my Hyper-v manager the server starts shutting down. I only have this with this one server (it runs Exchange 20 (HowTos)