It's hard to figure whats happening with so little information. Can you post some screenshots showing your cage, normal map, complete baking options, lowpoly/highpoly list.... and... how did you model that mesh? how was exported?
What was the smoothing options when you baked? What are they when you preview with normals on? They need to be the same. Also you may need to increase smoothing to remove some problems.. and gaining a few new ones. Erh.. and I'm talking about the lowpoly mesh. This is just guess cause it is usually what gives me problems.…