Hey Benni,
I just did the same thing you did -- I converted a Win 8.1 Pro laptop to a VM using the VMWare Converter. My host is an iMac (OS X Maverics), and my mouse is plugged into my keyboard. So I was surprised (heartbroken?) when I booted up the VM and the mouse worked when the keyboard didn't.
I made the registry change you suggested, rebooted, and everything worked fantastically well.
Thanks as well, of course, to cojaxx8, who originally discovered the solution.