It might because you packed the pck file inside of it that it doesn't like it. I was able to open it and play a little bit just now. I got to the part with big floaty heads and killed them all, but when I went to the rocket it seemed to crash. Also, not sure if this was intetional, but the tank appeared as a untexture cube. Let us know when you get the file thing figured out. I'd love to give it another whirl!