Help! I need that patch too, because the same is happening to me, even if I'm on 2D Toolkit v2.3.3 (and Unity 4.3.3). Unity crashed badly, and when I reopned it it started to throw billions of errors. I managed to fix the issue, but now I get the error the OP posted. Also, the SpriteCollections are actually in the Project folder, but every sprite name has been renamed to random numbers, fonts included.