I have a X1 carbon gen 4 with an Intel 8260 wireless chip. I am using windows 7 x64 professional.
I followed the instructions provided by Intel to replace my Bluetooth driver.
4. Install the new Intel Bluetooth driver.
5. Re-install the Microsoft KB as needed.
I could not get step two to work with Intel Proweireless Driver 19.1.0 installed. In order to get the new Bluetooth driver to install, I had to roll back the Intel Prowireless Driver to version 18.40.2. I did this by using my imaging software to reload the operating system with the older version of the Prowireless software. With version 18.40.2 of the Prowireless driver installed, I was able to use the Intel Bluetooth Driver Install Instructions and get step two to work. Once the Bluetooth driver was updated, I reinstalled Prowireless driver 19.1.0.