Slightly OT: Can't boot Win10 VB guest on Xubuntu 22.04

[MR ZenWiz]

Yesterday I ran some updates for VirtualBox to release 7.0.18, and my
long-time running Windows 10 VM suddenly won't boot at all.

I've asked a couple of questions in the VB forums, no response yet.

If anyone here has any suggestions, I'm open.

Most recently, VB complains that it can't find a bootable image (this
is completely unchanged since it's been running merrily until
yesterday).

I was looking for a way to "upgrade" the VM, which is set up for
legacy boot, to run with a UEFI boot. That failed miserably, but I was
testing this on a clone of the original Win 10 VM.

Now the original, unmodified VM won't boot either. I have filed a VB
bug about this, too.

???

Mark