Bug#787794: lifimage fails to successfully boot on hppa
Could you please try to boot this lifimage:
It's the same as the other lifimages, but all 64bit Linux kernel related drivers were dropped.
Additionally it's without USB drivers and some other things which should not be relevant for 712/715 machines.
I suspect out-of-memory situations with the other lifimage on your machine, since my machine has 160MB RAM and there does it boots.