Probably a crazy question - but are you totally sure that you only have ONE blade in your cutter? Twice in the past several years I have replaced blades in my Olfa cutter and realized, after bad, bad, bad cuts, that I had 2 blades in the cutter. They are so thin, and seem to stick together so well that it is not a hard thing to do - to put 2 stuck together blades in the cutter.