Hm, this looks a bit strange.. I have libffi4 installed, but apt-cache policy doesn't list the repo. That indicates that it's in the repo but not in the packages list. Don't know how I got it installed then, maybe it came with the July firmware upgrade? You can try to download the armel version (libffi4_4.1.0-1osso1_armel.deb), and then use 'dpkg -i' on the file to install it. (You may have to be root).

NB: In any case, make sure you have either the last (September) or the next-to-last (July) firmware flash update installed, if you haven't then things won't work anyway as far as I can see.