Hi! Refraction where things overlap was corrected in the Corona 4 core (works fine so long as the normals are ok, and may give a "different" look but it is actually more correct). In Max, there is a pop up on loading a scene created in an earlier version of Corona, allowing you to choose to use the new better refractions or stick with the old way - this dialog is not in C4D yet (but should be in the next daily) so you always get the new version. Could be there is a normals issue though with such a dramatic change - so options for now are to use a daily earlier than the Feb 20th one; wait for the daily that has the option to stay with the old (less correct) refraction; or check and change any issue with normals to get things working with the new refraction.