Viber is not supported on the LG Optimus 2X. Your phone runs Android 2.2, while Viber requires Android 2.3.6 and up
first of all our phone is running andrid 4.0 by lg and 4.4.2 by unofficial cm11 versions for our phone by tonyp. And he said, that he is using cm 10.2, which is based on android 4.3, isnt it?