Set default cropping-ratio for thumbnails in image editor

are there any possibility to set the default cropping ratio for thumbnails in the shiny new image editor? 🙂

i need my thumbnails in 240 x 135 everytime. instead of scaled images that fit the proportions i need them cropped. by default wordpress scale to fit them.

i tried to set this by putting the following line in my functions.php, but now the cropping feature in the editor seems broken: set_post_thumbnail_size(240,135,TRUE)
(3rd parameter for turning cropping on)

… now i can’t apply cropping, there are two fields with a value of “Infinity” and the save button is disabled. see here

i’m confused. 🙁

regards,
mathias