It looks like this is an NVRAM Locked issue.
There are several things that can cause this; including that some Windows Udpates can cause it to happen.
I agree with you; I doubt it was caused by anything that you were doing.
Sadly, this is an issue that has many causes and therefor, many solutions. You could try clearing your CMOS battery and checking your BIOS EFI settings. This is where Windows can actually interfere with Linux: Windows actually has the ability to communicate with and instruct a motherboard (Which has its own operating system: BIOS. BIOS is a separate OS from Windows or GnuLinux.) per its settings.
Other than that - since you say you have back ups readily available, if this was me; I would wipe and reinstall.
Save yourself the headaches and stress and get a fresh start.