ok, I have the same problem. O, K, M don't work. If I press furiously around O, it works once in awhile, but K and M only works when I do battery pull. But only works for less than an hour, and goes back dead. I really want to know what is causing this. I strongly think it is some kind of software issue, but then if you did factory reset and it still didn't work, it might be a hardware issue.
Just the fact that it works fine for a little bit after battery pull makes me think it's some(a) software that is causing this.
Everybody who have this problem, can you think of anything unusual thing you did before this problem occurred?
For my situation, I was taking whole bunch of video clips(some were like 20min long straight) until battery went down to like 4% remaining. Then I charged it in my car(with the Verizon carcharger) and found the keys were dead after driving for little bit. Other than that, I did updates on whole bunch of apps on google play the day before. I don't know what is causing this problem, but hope I can find a problem.