VirtualBox fails to load VM with code E_FAIL (0x80004005)

I'm using the latest version of VirtualBox 6.0.4 r128413 (Qt5.6.2) trunning on x64 Windows 10. Had been running a Windows XP guest for this morning, then shut it down. After an unrelated update to a Visual Studio installation, the VM now will not start with the following error:

Failed to open a session for the virtual machine WindowsXP.

The virtual machine 'WindowsXP' has terminated unexpectedly during startup with exit code -1073741819 (0xc0000005).  More details may be available in 'H:\VMs\WindowsXP-Dev\WindowsXP\Logs\VBoxHardening.log'.

Result Code: E_FAIL (0x80004005)
Component: MachineWrap
Interface: IMachine {5047460a-265d-4538-b23e-ddba5fb84976}

The VBoxHardening.log is incomprehensible, but I do note this question has a similar problem, though with a much older version of VB.

What is going on? How do I force VB to abandon the check for DLL versions?

This is very normal behavior if you have saved a session and then update VirtualBox.

You need to trash that active session, then it should work again. Also, make sure you update the extension pack for your new version, or this error will pop up too.