recently got an '04 Tassajara. It's my first "real" mountain bike. I took it to the shop to have the derailleurs adjusted because I noticed this skipping problem. They said they fixed it but I'm still having the same problem. It doesn't do it in all the gears just in the lower gears and only when I am peddling like normal (when I pick the back tire up it doesn't do it). I am hoping that someone here knows more about derailleurs than I do. I am trying to learn how to fix it myself so I don't have to rely on the LBS for simple fixes. I appreciate any help you can give me.