Most of the protein powders are made of either casein or whey, which are milk byproducts. Some people claim that milk may be detrimental to PwMS, but whether whey in particular could be harmful I think is up for discussion.
I've settled on a decent compromise. It's a protein powder made by Garden of Life, and it is all vegan and raw. http://www.iherb.com/Garden-of-Life-RAW ... 22343?at=0
I actually just bought it at Whole Foods last week for about $31 and it contains about 30 servings, which makes it on par with the other powders out there. 18g of protein per serving. It doesn't taste heavenly, but if you mix it with a vanilla soy milk it gets better.