Error 0x80070005: Access Denied when first start Hyper-V in Windows 10 Pro

I'm trying to run Hyper-V on a freshly installed Windows 10 Pro (1709) on AMD FX 6350, 8 GB RAM. Hyper-V Virtual Machine Management (vmms) starts properly but Hyper-V Host Compute Service (vmcompute) crashes with the error Windows could not start the Hyper-V Host Compute Service on Local Computer. Error 0x80070005: Access is denied.

In the log only meaningless message The Hyper-V Host Compute Service service terminated with the following error: General access denied error.

Googling finds a similar error when migrating or exporting virtual machines, but not the first time Hyper-V starts with no VMs are created.

Previously, this hardware was Windows 7 and Vmware Player worked fine. Now I want to try "native" virtualization.

By the way, exactly the same problem on the laptop on Intel i5-2430M.

This is known to be caused by disabling Windows Control flow guard (CFG).

To turn this back on:

• Search for and open Windows Defender Security Center on the start menu.

• Go into App & browser control:

• Scroll to the bottom and click on Exploit protection settings:

• Ensure that Control flow guard (CFG) is set to On by default:

This morning my Hyper-V was working, then this evening it wasn't. Disabling CFG was the only noteworthy activity I had done on Windows aside from regular application use. After re-enabling the feature, Hyper-V was working again for me.

I disabled the feature in the first place due to an issue with Windows 10 build 1709 which is severely impacting my TortoiseGit performance in that the diff tool takes about 5 seconds to open.

Another users comment on that page reports the same problem.