Hi Ward,
Not sure why it would not work with the current virtual hardware settings.
However if you shut down the VM completely (not suspend, but shutdown) then you can change the virtual hardware / compatibility settings to an earlier version.
Just checked my Yosemite VM and I have it set at version 11.
Also uncheck that "Allow upgrading the virtual hardware..." checkbox at the bottom, so that you don't get that nagging popup all the time.
--
Wil