The white render I think I can explain. The new settings in V8 for Exposure etc. aren’t fully backwards compatible, thus you would need to adjust the exposure settings to avoid an over exposure from the Sky I use to light the scene.
The displacement issue I think I can explain, too. Before V8 (IIRC at least), only the displacement of the base material of a layered material was taken into consideration, this has changed.
If you cannot switch to V8, a simple fix would be plugging the material with the displacement in the base material slot and the other one in the slot for material 1. You would have to invert the vertext map, too, of course.