I'm not sure what happened either! Does it froze at the same point everytime?
I know there could be a random bug saying "header not found", but it's random (probably because of the game making engine) so i don't know how to fix it...and it may be not very stable on win7.
I haven't got any report on the light version...Try restart it and don't run too fast/use the menu too fast, if it's still not working maybe you could try it on another computer T^T
Very sorry for the inconvenience!!