It appears the errors in the VirtualBox log are normal. The following are from starting a Window 7 x64 VM with a mapped USB device:
00:00:35.054000 ERROR [COM]: aRC=VBOX_E_INVALID_VM_STATE (0x80bb0002) aIID={22781af3-1c96-4126-9edf-67a020e0e858} aComponent={Machine} aText={Machine is not locked for session (session state: Unlocked)}, preserve=false
00:00:35.834000 ERROR [COM]: aRC=VBOX_E_IPRT_ERROR (0x80bb0005) aIID={22781af3-1c96-4126-9edf-67a020e0e858} aComponent={SessionMachine} aText={Saved screenshot data is not available (VERR_NOT_SUPPORTED)}, preserve=false
00:00:36.255000 ERROR [COM]: aRC=VBOX_E_INVALID_VM_STATE (0x80bb0002) aIID={22781af3-1c96-4126-9edf-67a020e0e858} aComponent={SessionMachine} aText={The machine is not mutable (state is Starting)}, preserve=false
00:00:38.033000 USBPROXY usbLibDevCfgDrGet: DeviceIoControl 1 fail winEr (31)
00:00:38.033000 USBPROXY usbLibDevCfgDrGet: DeviceIoControl 1 fail winEr (31)
00:00:38.049000 USBPROXY usbLibDevCfgDrGet: DeviceIoControl 1 fail winEr (31)
The VM functions normally so I assume the above messages don't mean anything or do they?