RESOLVED: Can no longer boot into my separate Windows volume

[PowerMac G4 MDD]

I updated to Mojave, on my 2009 4,1 (5,1-firmware flashed) Mac Pro, and I can no longer boot into my separate Windows 10 disk. At boot-up, the screen remains black and no progress is made. (I don't have a flashed card, so I cannot check for any activity.)

A recent article mentioned that a specific model / configuration of iMac will no longer have Bootcamp support, under Mojave, but that doesn't make much sense. For one, Bootcamp is NOT a necessary tool for installing Windows. (In fact, I never used it when installing Windows on my Mac Pro.) What could a Bootcamp incompatibility have to do with Windows, in any of itself, running on a Mac? Secondly, nothing should be holding my Mac Pro back from booting into Windows—if, indeed, there's somehow a preventative force for installing Windows on certain Macs—because it's not listed as incompatible. This must be some odd glitch...

Any suggestions? Thanks.

 

[PowerMac G4 MDD]

Edit: looks like a sporadic Windows update was compromising the boot procedure and leaving me with that black screen. On the third try, I was finally met with a sign of life, from Windows: an update-progress screen. Following a restart, it was fine and dandy—it booted to my desktop.

How did I not guess that Windows was behind pain and suffering (as usual)?