JP8851 has provided a new BIOS version for people who have the Taichi21 or 21a (answer marked below) . The BIOS version is not official yet, however, and many users are reporting problems with the BIOS update such as USB problems, pen digitizer problems and audio problems. Therfore I have still marked this problem unsolved, but the first answer below may work for you.
THIS IS A PROBLEM YET AGAIN.
ASUS, MICROSOFT, AND INTEL: HUNDREDS (IF NOT THOUSANDS) OF USERS ARE FRUSTRATED BY YOUR LACK OF SUPPORT AND COMPATIBILITY CHECKS WITH EVERY UPDATE. WHY SHOULD A $1000+ LAPTOP BE NEGLECTED THE PROPER "V.I.P." SUPPORT WE WERE PROMISED? PLEASE FIX THIS PROMPTLY, IT IS FRUSTRATING FOR THE USERS TO FIGURE OUT WHAT GOES WRONG EVERY TIME WINDOWS UPDATES.
Previously, the Asus Taichi had problems with the back screen not working after the windows 8.1 update. Recently, Micrsosoft released a NEW UPDATE that ruined the fix mentioned below, and all the supposedly long term fixes Asus made with the bios
updates and the graphics driver updates.
This problem had originally been solved for windows 8.1 (without update 1) by downloading the following old graphics driver from the asus website: