The ONLY version I got to run, was a single version of 4.2.19 that I found a while back after trawling the bug tracker and found a link, it had some tweaks and that was clearly the problem, however whatever that fix was, it's not in 4.3
Guessing this is the key: usbLibDevCfgDrGet: DeviceIoControl 1 fail winEr (31)
Here is the VBoxSVC.log
Thanks.