Lyp-Sync Problem

Hi! I have a strange problem. I have 4.5 Toom Boom Studio installed and the problem is that when I click on the “Modify Lyp Sync Mapping” and try to change the layer where the mouth is (Example: Layer:Front Backgroud for the one named “Mouth” which is a sublayer of Body>Head>Mouth). And then all my layers disapears for a second and the sound don’t change. Wehn I click again on “Modify Lyp Sync Mapping” the layer is again the first one and not the one named Motuh that i seleced. Am I doing something worng?