Virtual box Debian Stretch boots to blank black screen

[JDABronx]

I have Debian Stretch Raspberry Pi OS running as a guest under VirtualBox. It was working perfectly for a few weeks. Recently, I shutdown the guest, restarted it and it is now booting to a blank black screen. This has happened before and the only thing that worked to resolve this was to re-install and start over.

Questions:
1) Are there a detailed set of instructions I can follow to diagnose / troubleshoot what is going wrong?
2) Is there a post in this forum that will provide me with guidance on how to solve this issue? Searches yield only generic suggestions and nothing that has worked so far.

I really don't know Linux that well so the more detailed the instructions the better.

[scottgus1]

Start the guest from full normal shutdown, not save-state. Run until you see the problem happen, then shut down the guest from within the guest OS if possible. If not possible, close the Virtualbox window for the guest with the Power Off option set.

Right-click the guest in the main Virtualbox window's guest list, choose Show Log. Save the far left tab's log, zip it, and post the zip file, using the forum's Upload Attachment tab.

[JDABronx]

I zipped the saved log. Uploading here.

[scottgus1]

Hyper-V is enabled. See HMR3Init: Attempting fall back to NEM (Hyper-V is active). (The new test builds might have a fix for this problem. If you try a test build and it works, report here: viewtopic.php?f=6&t=90853, and save the installer file.)

[JDABronx]

Earlier, before I posted here, I had tried un-selecting the following from Windows Features:

• Virtual Machine Platform
  Windows Hypervisor Platform

This did not resolve the issue. I don't see any option for deselecting "Hyper-V".

[JDABronx]

I followed the instructions to turn Hyper-V off. When I type bcdedit the report says "hypervisoorlaunchtype Off". Same problem though when I start the Debian VM still a blank black screen.

Sending new cut of the log file

[scottgus1]

Hyper-V is off now:

00:00:02.618056 HM: HMR3Init: VT-x w/ nested paging and unrestricted guest execution hw support

Hyper-V has been the usual cause of guest seize-ups, but not the only cause. Some have reported they could still SSH into a Linux guest showing just the blinking cursor. Meaning to me that it's just the Linux GUI that can't start. Try increasing the guest's video RAM.

[JDABronx]

I increased the video memory from the default of 16MB to 64MB and still showing a blank screen.

[scottgus1]

Try changing the video card to VboxVGA (no S).