Sounds very similar to an issue I am having. After revisiting the cove with that fellas head its impossible to save the game without it crashing. I'm playing exclusively coop in this game which I've found somewhat more unstable than single player.
I have also hit a second crash point like above where after defeating that big fire daemon and getting hit by the stone, when I transport to the hall of time it's no longer possible to save without crashing.
If you email me I can reproduce the faults pretty easily(I have also submitted bug reports after the crashes)
