Hi,
I have the problem, that when I want to use sculpt mode to add some details for my low poly models for baking, I can add some multires levels, but when I acctually created the details, I wanted to bake (which worked) and go back to level one, the lowest poly character… the mesh was gone, level 1 looked like the first level of multires applied (round), not the original character I created. So, how can I get back to “level 0” then?!
In multi-res when you move the vertices on higher levels you also move the the vertices on the lower levels. That is if the vertices you move also exists on the lower level.
You might want to save the model before going into multires and then apply your bake to the old model. I know that it might not help on your current project, but on future ones it might.
actually it appears without modifiing anything… 
So, well yea i thought about just duplicating th emodel before sculpting after I posted. thanks for confiming that 
ah, you want to turn the multi-res off? goto level one and apply it. maybe even delete all the higher levels.