Thanks all. Here are the answers to some of the questions:

1. I have the stock Shimano wheels that came on my 2007 Scattante: Shimano WH-R561-L, 16H front and 20H rear.

2. I am 6' and weigh 195.

3. I have adjusted the brakes a little looser, but I don't want to go much more. I really don't want to open the releases for downhills.

4. After reading the responses I am certain whether it is the frame or the wheels.

5. If it is the frame, I will examine the chain stay. I will also look at the spoke tension.