I have the question also about similar problem.. if anyone can help my ill be thankfull alot ... so when im rendering all the materials who are not in group are just deleted somehow.. so if someone knows about this kind of problem please tell me ...
here is after rendering the last time
https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xap1/v/t1.0-9/10734254_10204458854332520_1746582696066770282_n.jpg?oh=5d09c77ef45ee0f97720928c535b2f65%26amp;oe=54B32A51%26amp;gda=1421666820_8d243cf8196727c302c7989abfe2d005
and this is render before this error come to my program