Well any object with the skin modifier needs to have all vertexes with a wieght of one. I presumed you are merging the cloak to the body, which is why I gave you a link to that tut. However if you aren't merging it to the body and only linking it to a bone all you need to do is remove the skin modifier from the cloak. The easiest solution with a simple object like a cloak is to map it manually. It can take longer but it's less confusing.

I don't have time to write a full guide to vertex mapping and I'm sure there are some around, I will try to find one on pixel2life and post the link here later.

Sundjata Kieta