I have LR 5 on my Macbook pro and I noticed the sliders used to make changes to my picture (exposure, contrast and etc), stopped working. I can slide the sliders left and right, but it will not make the changes to my picture. Example, changing my exposure from 0.20 to 0.60 will not make my picture brighter. It doesn't change anything. However, I can still change my exposure using my mouse over the histogram. Help!