I also can't view the ending cut scene of Episode 3 with Episode 4 installed; the game freezes during the scene transition after getting the silver moon (both with the patch install and the full install; I had to switch to the latter since my C drive ran out of space during patching and that seemed to corrupt the game; the main menu still thought it didn't have episode 4).
That is, I can't see the Episode 3 ending when I use a save from a previous run-through. I went back to get the baby suffer, which I missed the first time, but I used a save right before the point where I couldn't get it anymore. Upon a few failures, I gave up only to notice you couldn't "continue" the game any more. So I can't keep all of the

's in my inventory through all the episodes.

Oh well, I understand that feature caused some issues anyway.