Later on in the day, I plugged it in to charge and I went to make it brighter.
It was not on the charger when I did that and I was in a darker room so I had the brightness down lower. After I hit the Fn + Home and adjusted it to my preference. I just got the x120e and I already went through and fixed it auto-brightening itself.
Lenovo X Series ThinkPad :: X120e Funtion Keys For Brightness Not Working? Mar 29, 2011