Can't find a place to submit a bug report. So here goes.
Full Error Message:
Windows cannot load the device driver for this hardware because a previous instance of the device driver is still in memory.
Windows 8.0 x64
Vmware Player 6.0.1 build-1379776
A USB keyboard ceases to function on the host operating system following the first host OS reboot after installing 6.0.1 on Windows 8.0. This issue does not occur with 6.0.0. The issue disappears upon uninstalling Player 6.0.1. Reinstallation allows Player to operate as expected, but issue re-appears after host OS reboot.
The issue happens immediately after host OS loads, and continues irrespective of whether VMWare Player is launched.
Looking at the keyboard drivers, the usb keyboard's driver has not loaded (see attached images). The built-in keyboard driver however reports no errors and continues to operate as usual.
Changing the USB keyboard device to that of a different manufacturer does not resolve the issue. Any USB keyboard driver appears to fail.
1) Launch msconfig
2) Disable VMWare USB arbitration service
4) USB Keyboard works. VMWare Player continues to operate as normal, minus the ability to mount USB storage devices on the guest OS.