So I've just started playing Enslaved, and I'm enjoying the game so far. However, I seem to be stuck at this one particular point in chapter 3 where you're introduced to the gattling gun bots. After finishing the robots off, the game then prompts me to go over to the ladder to lower it for Trip. So I go over and do that, and then Trip comes over and stands by the ladder (slightly clipping into it), and then...

Nothing happens. You're both just standing there, you're not able to control anything (you can't even pause the game), meaning that the only way to close the game is for force quit in the Steam overlay. I wouldn't even call it freezing because the AI just stops dead in its tracks by the ladder, but the models, camera and some of the textures are still moving. Why is this?

Thanks in advance for any advice.