Why does my Page in a page flip animation created in maya go grey when the animation is run?

I’ve created a book with a page flip animation in Maya 2012, I’ve imported it into Unity added the textures and the Normals are all in place.

My problem starts when I run the animation, the page as it turns starts to go grey, and when it is flipped the page is a dark grey.

I’ve tried different light sources, checking the materials, confirming the normals, but nothing helps. When the animation isn’t run both sides of the page are as they should be.

What is happening, and how can I get it to run as I would like?

Is this, by any chance, a shader with culling turned of, and these pages are single two-triangle polygons? If so, it is no wonder that the turned page is dark, because light comes from the top, while the polygon looks downwards. The backfaces of a polygon are not illuminated.

Below is a screenshot of the underside of the book where you can see the page is shown with the texture. So there doesn’t seem to be any problems with the polygons looking downwards.