WOO! I figured out the bug.

It's *actually* caused by opening up the notebook before you go to the dorm. If you never opened up the notebook before the dorm, then this bug never happens.
For those interested in the technical side of things, looking at the notebook before the dorm increases the "tutorial count" by an extra number then it should have, so when it looks for the next tutorial message it crashes (whether tutorial mode is active or not).
So sorry that I released the game with this horrible bug, but I'm happy that I narrowed down on the issue.
Funny how you could test a game ad nasuem but never find the most obvious thing.
Anyway, as I said we are fixing it and retesting the game now. Then we'll get an update to Steam sharpish and cross our fingers that they implement it right away.