Been there, done that.  : ) It's very sneaky, because you just have to hover over a setting for the scroll wheel to be active. You could have the mouse pointer resting at one spot and be looking at another, roll your finger on the wheel in thought and later be surprised. Since then I double check summaries to be sure nothing looks off. 

On the other hand, scroll is a good thing if you want to see the changes a setting makes on the pattern piece very quickly.
Shel