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Windows 8.1 Pro Media running VM 4.3.26 r98988. When I start Windows 2012R2 the host keyboard stops working. I can still use mouse, but have to use the on screen keyboard to continue. Once I log out, my keyboard does not come back for my host system. I do a hard boot to recover. Other systems launched in VM does not have this issue, i.e. Linux, WinXP Pro.

This usually means that you've set up a blank USB filter, a filter that matches any device and assigns exclusive ownership to the VM.

It could be any USB device at random, in your case it's the keyboard.

Make the USB filter non-blank - i.e. add the minimum number of fields needed to identify whatever device you intended.