Err, not blurring, but the between pixels were smoothing out the motion. Now that it's pixel perfect, you can see the movement in little jerks sometimes.
In your draw events of your object that are moving at fractions of pixels have you tried wrapping the x and y in floor? So for example draw_sprite(sprite_index,image_index,floor(x), floor(y))
Sorry if you have. I just thought it might help with any juddering and such. :P
