Hello, I had similar problems with this ultrabook, thought I'd detail how I fixed them. I dropped my Zenbook a month ago and the only effect was that various keys on the right side of the keyboard would not work for periods of time. Eventually, the Power button stopped working and when I let the battery run out of charge once, I could not turn it back on. I hunted for information online and eventually found this great guide, where a guy with similar keyboard issues fixed his UX31A keyboard:
http/www.ifixit.com/Guide/Unresponsive+Keyboard+Keys/11932/1
I went to a local tool shop and picked up a screwdriver kit with a Torx T5 head and followed his instructions to re-insert and tighten the keyboard connector, which had come loose just as shown in his photos. After that, I was finally able to turn my Zenbook Prime back on and I have since had zero problems with the keyboard, just as before I dropped it.
Probably not a good idea to use a Power key on the keyboard when your keyboard connector is so easily dislodged, Asus. I guess they had to cut corners somewhere to offer such a fantastic ultrabook at such a great price- the Zenbook Prime UX31A-DB51 is the best laptop I've ever had- and taping the keyboard connector into place is the result.
I read all the Amazon reviews where users complain about the keyboard; not sure why their support guy who responds there keeps blaming the software and tells them to do a factory reset of the OS, when it's most likely this hardware issue, although perhaps there are software issues for others too.
If others who are willing to open up their ultrabook can try this fix out and post their results here, we can see how many people are affected by the same problem. It was a very easy fix for me, once I bought the Torx T5 screwdriver: just reconnect the keyboard connector, as shown in the photos. I'm glad I fixed it myself, as sending it back to Asus would have been a hassle, and who knows if they themselves realize this problem, considering their support guy keeps blaming the software on Amazon.