Add LTspice IV library to LTspice XVII
I'm only 75% sure that this is the problem, but it's the problem I had when I moved to the new LT spice. 

LT spice uses a new directory, stored in documents\LTspiceXVII\lib (not in C:\program files\lt spice\lib).

Make sure you modify the files there and not in the program directory which has a dual structure, but LT spice uses the files stored in documents folder.