OK, thanks for being so patient with this..
The fact that it does the same in safe mode now mostly eliminates any other software interfering with the process.
One last thing I would like you to try, it's a long shot though...
Download the ptogram in the link below:
http://www.nirsoft.net/utils/usb_devices_view.html
Delete all references to attached and previously attached USB devices - WITH THE EXCEPTIIN OF YOUR KEYBOARD & MOUSE (for obvious reasons)
Then also go to the device manager and delete all the USB ROOT & HUB devices, including the motherboard ones... This might get tricky and you might lose use of the keyboard & mouse.
If that happens, just switch off & on again.
Then go back to device manager and "Scan for Hardware Changes".
This will re detect and install all the detected devices. Then plug in the external drive again and try it.
That's all I have I'm afraid... Sorry mate..