Alright, to test out whether it was the saves that were the problem I decided to create a new game and skip ahead to chapter 3, then click Play.
It asked me whether I wanted to generate random choices, I click Yes. Now, here's the weird part, it asks me whether I want to rewind my choices, even though it's a completely new game! Image.
Clicking either yes or no just leads back to the black screen, and I have to force shut-down of the process.
Edit: I fixed it!
Although it was really damn lucky. Episode 5 got released a couple of minutes ago, I deleted ALL MY SAVES via the in-game delete option, (they were all backed up in case though) and then created a new game. I said stuff it, I'll play it with random choices, I just want to see the ending to this saga! After starting up a new game it asked if I wanted to randomize the choices, I said yes, and, well holy shit, all my choices are there. Doug was saved, Clementine has no hoody, Ben is dead, Kenny didn't come with me.
Either this was one freak coincidence or it somehow works after this. I'm really glad.
For reference for anyone reading this, I tried starting Episode 5 with my saves un-deleted and it gave me a black screen.
Sorry for the hasty spelling/grammar, the game literally just started, I'm just so excite! Squee!