All,
I hope you have all raised a support case on the support site (which was what I did... and even though they didn't solve the problem for me - I found a solution myself - they did eventually respond) so you will get a one-to-one support.
Can I suggest, that even if there is no exclamation point in the Windows Device Manager, that you at least try reinstalling the driver for the CPUs... maybe by letting Windows go to the update site (this time only) and install automatically. Or even rollback. Just because there is no exclamation point, doesn't mean it is not the same issue.
One last thing... I assume you have all checked Windows Task Manager and made sure nothing is running on the VM? This is the first thing I checked... I had virtually NO CPU utilisation within Windows, yet the parallels app was taking 100 (or 200) % of my Mac O