There may be an issue with a spell that is making the inscription table crash. If you delete the ars magica config file, will it autocreate it? I am wondering if when you updated then reverted it added a spell to the config that is not in the current version or something? I read the code and backtracked it through all the minecraft code, which is a huge pain in the ass without any comments since I used a decompiler. The part of the code that crashes the game is when it is searching for your current spells to display on the table. It must hit a spell that has a null value. I will keep digging through the code to see what else I can come up with.