Martin,
I don't know if it is going to help you or not but you can do it in following way:
1. Go to device manager uninstall the driver by right clicking on the ""TI CC2540 Low-Power RF to USB CDC Serial Port (COM9)" .
2. Disconnect the dongle and connect it again, it will appear as "USB Device"(with ! mark)
3. Windows will promt you for driver installation:
a). Click on "Yes this time only"
b). Click on "Install from specific location(Advanced)"
c). Select " Serach for best driver in these locations" then select "Include this location in the search"
d). Now choose this exact path "C:\Texas Instruments\BLE-CC254x-1.3\Accessories\Drivers\"
e). Click on next.
4. Finish
Hopefully this will install the driver properly. Do tell me if it works!