If you’re getting extra tearing or other bad cutting behavior, you should try cleaning out your blade holder before chucking it out in anger and getting a new one. Take it out of the machine and ratchet the blade to 0. After that, hold it in your left hand horizontally with the blade side outward, then, with your right hand, push inward and twist off the white cap by turning it toward you. It should easily come off and the blade will be exposed. Just tap the paper scraps gently out and then maybe use a Q-tip if there is still some left.
Check out what I found in mine!
I found this tip out on a youtube comment on this video. If it is your sort of thing, you can head over there and thank Kip. ^_^
UPDATE October 7th, 2013:
I tried this with my blue blade holder and I can’t get it to unscrew. When you press inward, you should feel the cap already give a little and then easily come off. Do not try to force it to come off!
I examined both of the blade holders and they look identical except for the coloring. So, try and see if you can take the cap off and tell me about it.