As NCW 164X said, you are not unique, there is a constant stream of people posting here about being banned by AdSense.
Invariably the poster has, like you, made very few posts on WebmasterWorld. Very few regular members have been banned, and as far as I can recalled, no regular member has been permentantly banned without reason.
I those instances where WebmasterWorld members have had some data to work on, in the majority of instances it has been shown that the website that had been banned was, to say the least dodgy.
If you have a legitimate problem, then take it up with Google. If there is fraud or other breaking of TOS, then I would say they are quite at liberty to retain the earnings for January.