Alpha issue with mib_volume in Maya 8 Mental Ray

Progg

For anyone that has experience rendering with mental ray I have an issue that I need help resolving. I am using a mib_volume shader attached to a camera in order to render distance fog, and everything is fine until a model with a transparency map is put in from of the fog... then the alpha becomes 20%'ish visible where it should be 100% transparent. In Max I think you can fix the problem by using the arch/vis shaders but I am in Maya 8.

Any suggestions would be helpful.

Thanks