I had the same issue. I found this online: http://answers.microsoft.com/ru-ru/windows/forum/windows_7-hardware/%D0%BE%D1%88%D0%B8%D0%B1%D0%BA%D0%B0-%D1%81/be8247a4-d230-42d9-a1cd-f548409acb5a?page=2
After restarting (F8) in a mode that disables digital signature verification, I finally got a connection to Hamachi, but now there's an exclamation mark next to all users that won't go away.
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