Did you use color catchers when you washed it? I always throw in one or two, even if the fabrics have been pre-washed. Also, did you notice the bleed before you dried the quilt? The heat from the dryer may have set the stain.

There is a product called Synthrapol Detergent that might help. It is supposed to keep the bleeding colors from setting into the other fabrics. http://www.dharmatrading.com/html/eng/2127-AA.shtml It can be purchased online as well as at many quilt shops.

Maybe try soaking the quilt in cold water for a while and rewashing it with Color Catchers until it looks clean. Don't dry it again until you have tried everything. Heat sets stains.