mental ray materials disappear in viewport

[alias_marks]

Hello, I hope all is well. I'm having some trouble with mental ray materials

 

When I'm trying to UVW map some materials or even just see them in the viewport I click the "view material in viewport" box and it shows up just fine...until I change or rotate my view. The material disappears from the viewport as soon as I pan or rotate my view.

 

I've made mental ray materials for all my objects and they are just shown in a dark gray tone in my viewport.

 

I've set all them up as DGS materials with a diffuse map.

 

Any ideas?

 

Here's an image to help clarify.

 

 

Thanks for looking

 

Michael