So the problem binding was made separately? (Not quillow fashion?)
Binding is more likely to ripple if it is cut on the bias. Most of us cut binding on the straight-of-grain. Bias binding is better for quilts that will get heavy usage (edge will hold up longer), but is not necessary for wallhangings or regular-use quilts.
You will probably need to remove the binding to get it right.
The biggest tip I can give you is to heavily starch the binding before you sew it onto the quilt. Actually, I heavily starch the fabric before cutting the binding! Starch stabilizes the binding so it won't stretch out of shape.
The other "biggest tip" I can give you is to use a walking foot to attach your binding.
Also, did you pin your binding in place before sewing? You really need to do this to make sure you are not stretching the binding out of shape as you sew. This applies to adding borders also.
I find it more difficult to sew a binding to an already-cut quilt edge, so instead I mark the quilt edge with a permanent Sharpie and pretend it is the cut edge as I sew on the binding. I don't actually cut on that line until after I have sewn the binding onto the front and need to roll the binding over to the back.
Here is a Youtube video of how one quilter handles binding:
http://www.youtube.com/watch?v=4PE0Yq9iGlc (3 parts to it)
and here is another video of how one quilter attaches binding completely by machine:
http://www.youtube.com/watch?v=wprg5vzkuGw (2 parts)
I think you will find them both very helpful!