Comment 5 for bug 897680

The basic idea here is that installing libc-bin:i386 is removing libc-bin and thus the system gets in an awkward state (here, it's that libc demands libc-bin, but there is no version of it installed after removing it).

You can reproduce this most simply by just running:
sudo apt-get install libc-bin:i386

Which removes libc-bin and fails to complete because ldconfig is not in PATH.