Try assigning a new material to the high poly and give that a go - I think (not too sure) that if you have a diffuse assigned to the material, and bake from that - it will also include the diffuse bake that in to it
It looks like the bake might be assigned to the wrong UV channel or something like that? What does the actual normal map look like? Edit: Hmmm but I can see the normal map bake from the high sort of underneath the mess here so that is weird, its almost like there is another tiling normal map on top of it or something like…