Ncloth problmes

I have been trying to do shot 19 in heroes1.0 where the kid uses the blanket as a cape, but every time I seem to take a step forward I then take three steps back, its really starting to slow the rest of my work down. the problem im having that that the cloth is not colliding with itself so it deforms through its own mesh. which is not going to look good in such a well prepared film. i don't want to let the team down due to this problem,