OK... this isn't very reassuring. I've just upgraded to Parallels 12.0.0, from the latest version of Parallels 11, on my MacBook Pro (Retina, 13-inch), running El Capitan 10.11.6. The laptop is connected to an external monitor via HDMI and I usually run it with the laptop lid closed. Before upgrading, Parallels ran my only VM, a Windows 10 machine, without a hitch. After upgrading, the VM refuses to launch, or rather: it launches but I get nothing but a small window with the VM's title but no visible content in the window. Activity Monitor says that the VM is using 90% of my CPU load, so *something* is happening. But the window sat there, blank, for 45 minutes before I closed it. Did this twice without a different outcome. So I'm stuck now, with a VM that won't, um, M. Any advice?