Magic TrackPad Won't Tap to Click

I own a mid-2007 MacBook with 2 GB RAM, 120 GB hard drive, and Mac OS X 10.7. I have everything fully updated as far as software goes. This Christmas, my parents gave me a Magic TrackPad. I had asked for one so I could use Lion's multi-touch features, and my computer's laptop isn't multi-touch. My Magic Trackpad works in every way but one: I can't tap to click. I can only manual click my trackpad by pushing those little buttons on the bottom corner. This is rather inconvenient, because then I have to use my trackpad on a hard surface. Usually I'm just sitting on my couch or I'm spread out on my floor, which is carpeted. Any suggestions as to what's wrong? I've gone in to all the settings; I have tap to click selected. I haven't been able to find anything in the discussions that's the same as my problem. Help would be greatly welcome!