Pixel Art Blurry?

Something very odd is happening!

I'm trying to animate with very basic sprites. I create graphic symbols out of each position, then create a movie clip with each graphic per one frame. But here's the weird part: Although the animation is fine, some of the frames are blurry! If I zoom in to 200%, the pixels are sharp. Yet at 100%, 4 out of 6 frames are a tad blurry.

I have the original sprite image set to Lossless and Allow Smoothing unchecked. What am I doing wrong?

I'm not an expert on this by any means, but if my memory serves... Make sure the position of the art is on whole pixels (ie 452.0, not 452.3).