Windows 11 “PROCESSOR START TIMEOUT” BSOD on Parallels

The first time I opened my Windows 11 virtual machine after upgrading to Parallels 20.2, it wanted to reboot the VM to upgrade Parallels Tools. OK, sure, makes sense. I clicked OK. It started shutting down, installed the updated tools, and started to reboot…but failed with a note about how it was diagnosing the system, and eventually showed a bluescreen error with the stop code PROCESSOR START TIMEOUT.

Troubleshooting and repair steps didn’t fix it. Neither did restarting it. Just as I was about to try uninstalling the latest update, I decided to try one more non-desctuctive approach.

I turned the VM completely off. And then I turned it back on again.

And it booted just fine.