Bummer! I hate that, especially when it's a wall hanging or quilt that is much loved. Any chance you could post a picture?
Without seeing it, if you want to salvage it, perhaps you could use the fabric paints to touch up the colors.
Was this old fabric or fabric from some place like WalMart or is this fabric that you got at a LQS for $9+ a yard? I know the less expensive fabric can really fade fast.
Do you wash it a lot? If so, what type of detergent do you use? I know a lot of the detergents we use for washing clothes have a chemical in them that fades fabrics over time. I can't remember the name of the ingredient at the moment. I'll have to see if I can find it.