COQUE element problem

Hi everyone,

My case is fairly simple, and yet I am experiencing troubles:

I model a simple plate (150*74), and assign a composite material to it (sandwich actually). I apply my conditions on 2 of the edges, apply gravity and run. When I check the sum of the load on the Z axis, I do not find my weight * gravity... I have tried with isotropic material and it works fine. Yet as soon as I apply a composite, even if the materials are the same I do not find my weight again. Do you know why is that? I enclosed my .comm file and my .med file.

EDIT: I cannot upload my files, ho do I do?