Not being familiar with your plotter, this is just a guess. It sounds as though your software is set to do a pounce pattern, rather than just cutting. If you are getting dashes all the way around each letter or piece of clipart, and if the blade is "chattering" up and down all the way through what is supposed to be a cut, then I would bet it is set to "pounce."
Can't tell you how to change the setting on your machine---maybe someone else will come in on this.
Hope this helps.
bill preston