im 99% sure this is the bug, if you are going to use a flatificator terra former to bring land downwards to make it flat (not sure about raising it) it wont flatten the land that has the new long grass on it, do you end up with something looking like this -
http://www.mediafire.com/imgbn…86f7766b0d5049601006g.jpg
hope this helps 
also on a side note, i dont know if this is a bug or not, but the chilling terraformers work EXTREMELY slowly, as in i have 5 of them working and its taken over 8 minecraft days to make approx 5% of the land into snow..... not sure why 
