Sculpt tools wok on a UV sphere, but not on my model I am making.

The sculpt tools work fine on a practice UV sphere that has had a modifier ( multiresolution ) and been subsurfed about 3 times. When I try to use the crease tool on my model to add wrinkles to the face it doesn’t work except if I get over a low spot that is running horizontaly when I am trying to put a wrinkle verticaly, it moves the low spot and makes it deeper but no vertical wrinkle. I have tried all the adjustments and it does not change. I am using 2.53.1 31068 release. In Windows XP Professional. I watched a tutorial
that ridix sent me a link to get it. It really help me understand the tools, but it didn’t tell me what is causing this problem. If anyone knows why this is happening, please let me know. :eek: