It was possible to get stuck in the game by not collecting a certain item by a certain point in the game (details below).
The fix applied means that if you are stuck because of this issue, the next time you load the game the missing item will appear in your inventory and you can proceed with the game. It is also no longer possible to get stuck in the first place.
The item that could be missed: Spellbook II
Problem occurs if the above item is not picked up by the time you craft the Advanced Wand.
I hope this didn't affect anyone - if it did, I offer my sincerest apologies.