Since tk2D 2.1, i can't remember if it happens with 2.0, any time I want to quit Unity or switch to another scene Unity always ask me to save the actual scene, even if I've already save it, but when i open a scene that doesn't have any tk2Dsprite Unity works normally.
I'm using tk2D 2.1 and prime[31] social networking in this project, but I am pretty sure thats it's not prime[31]