Show us what you are trying to bake, with your low and high. I'm confused what you are talking about exactly. The idea behind putting a Push modifier is so that you ensure that your low is under your high, but I'm not sure why you would be getting black renders. I'm lost on this statement.
I am currently working through 3d palaces awesome ED209 tutorial (hope its ok to say that) however i'm at the normal mapping stage and am getting a lot of normal map errors. To brush up I've been reading through the normal mapping sticky and there was one point brought up - when baking your normal maps in max (I'm using…