Problem to open a car file in the GP4 Builder - SOLVED

I converted a car from Rfactor to GP4 using Zmodeler 1.0 , saving the file in z3D and GP4 . When I tried to open it in the GP4builder , got this message : Exception EAccessViolation dans le module GP4 Builder 1841.exe à 001C8D6C . Violation d'accès à l'adresse 005C8D6C dans le module GP4 Builder 1841.exe . Lecture de l'adresse 083CC000 .
Please can someone tell me which is the mistake I have done ? Just to let you know .... the file is huge , could be this the reason for the problem ?
Thanks in advance



Edited 3 time(s). Last edit at 10/22/2016 07:50PM by rracunis.

check if your textures have an alpha layer.
if not, it could be the cause of this problem

Bingo , alpha channel missing in just one single texture ( mirror ) . Merci Bernaud