file_column crop

I can't for the life of me figure out how to get cropping working with file_column

   file_column :pic, :magick => {          :versions => {            :thumb => {:crop => "3:2", :size => "120x120!", :name => "thumb"},            :big =>{ :size => "400x300", :name => "big"}            }      }

gives me: invalid geometry string `'

any ideas?

tx