Didn't work. Kinda sucks that I can't get this to work.
Is it all done in Cycles? The cubes are flat with no shadows, so I was wondering if you were trying something rendered in Cycles Composited onto a Blender Render.
What's your Samples #?
What are your setting for the Material on the Knife?
What are your settings for the Camera? Depth of Focus could be the culprit.
Do you have multiple lights or 1 Big flat Light emitter happening?
Can you put a link up to download your Blend File? Believe me when I say this made me nervous to do when I did it the first time. It's a lot of work and you don't want someone to walk off with it, but it's hard to diagnose without being able to see what is actually going on in the file.
Please let me know if I can help or if any of the questions helped point you in the right direction.