From the Windows 2008 R2 host machine, I can run the Hyper-V Manager and 'connect' to the Virtual Machine. The window pops up with nothing but a gray background (clearly the same gray background of the log in screen), but no 'ctrl-alt-delete' prompt and no ability to log in. This was previously working fine.
Note that I can still make a Remote Desktop connection to the Virtual Machine and it works fine.
Thanks.