In blender, I know of no there is no difference between curves and paths.
I believe that a few things could be happening.

1) Make sure that the orbs are children of the curve
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2) See that Data > Path Animation is checked
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3) You might also want the Frames value under Data > Path Animation to be equal to the length of your animation.

If all of these are done, and it is still not working, please upload your .blend file.