VERR_FILE_NOT_FOUND

[FrankNatoli]

Running VirtualBox with Ubuntu on Windows 11.
Started Ubuntu virtual machine, transferred some files from Windows to Ubuntu, began to transfer files back from Ubuntu to Windows and virtual session disappeared.
Upon attempting to restart virtual machine get this popup:
Failed to open a session for the virtual machine Ubuntu.
Could not launch the VM process for the machine 'Ubuntu' (VERR_FILE_NOT_FOUND).
Result Code: VBOX_E_IPRT_ERROR (0x80BB0005)
Component: MachineWrap
Interface: IMachine {85632c68-b5bb-4316-a900-5eb28d3413df}
Apparently, something has self destructed.
Tried rebooting Windows, get same popup.
What to do?