Windows 7 VM stuck on black screen after Welcome logo

I usually don't shutdown my VM (just shutdown my Mac which suspends the VM) but for some reason figured I'd do that yesterday.
This morning, I had no luck restarting my VM. It boots up fine up to the Welcome message, stays there for ever (compared to a normal boot that is) and turns black.
I figured out that I could show the Task Manager but this is of limited use. For instance, if I click "Show processes from all users", the TM freezes (I can't move it around or switch tab, click buttons). My only resort is to shutdown the VM (which takes so long that I have usually to kill the TM for this to complete).
Starting in Safe Mode works, but that is of course of limited use.
Since I was stuck and pretty much condemned to revert to an old VM to try and do some work, I went ahead and let PD isntall its latest update (15.1.2), as my last experience had ended up in disaster, and this update was advertised so poorly and cryptically, that I was very suspicious.
This is did not fix my problem.
So here am I, stuck for the second time in less than a month, and seriously considering moving to a real PC (no way I am going to buy a MBP again anyway).
Oh and I am certainly not going to bother to ask for support from Parallels: been there, done that.

 

So I reverted to my one month old VM (saved after a disastrous update to Parallels 15.1.1 (?) and a similar reversion to a previous VM to get back in business) and the VM did not have any issue booting up.
I managed to get half a day of work done (having wasted one half trying to sort out this mess) and decided to reboot just to make sure things were working fine. They did.
I am wondering whether the problem may be due to some incompatibility with recent Windows updates?
I am bringing this up, as a user reported similar problems in Windows 10, which he assumed could be due to a Windows update (no feedback from Parallels, so this hunch could be completely wrong): https://forum.parallels.com/threads/kb4525236-for-windows-10-user-logs-into-black-screen.348674/

The updates currently pending on my VM are:
KB2310138
KB4484158
KB4484119
KB4484152
KB4525235

No KB4525236 as the other thread brought up, but the last one is close enough (remember, my VM is Windows 7, the other poster was dealing with Windows 10)... They are both dated from 11/11 and are both Monthly Quality Rollups and quite massive (thrice larger on W10).

 

Follow up on that saga

Yesterday, I noticed a bunch of updates available for Windows 7.
The dreaded (maybe unduly so) KB452535 was absent, replaced by an innocuous looking KB4530734 (big fat Security Monthly Quality Rollup for Windows 7 x64-based Systems for December) and a bunch of others for various other MS products.
I went ahead and performed the install. It looked like it would take a lonnnnng time, so I left the thing running.
Next day, Windows had shutdown apparently gracefully and I therefore fired up my VM.
Well, sure enough, after the welcome screen, everything turned to black. I went back to the thread I linked to above to check the little trick on Power management, and as soon as I pressed return after typing msconfig.exe in the CMD box, the desktop started to appear, with taskbar, icons and a full-fledge file explorer. I quit msconfig before even using it, as clearly I was back in business.

Something is not playing nice with the VM when it starts up...