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