Hi there,
I have a tree model, it's leaves have a color node (picture of the leaf) and Alpha Transparency node (with an alpha channel map of the leaf)

Using Maya software render, the leaves render out good, with the alpha channel transparencies working fine.
When I render with Mental Ray though, the leave just look like square jpgs, showing the color maps in full with the transparency maps not working.

Any ideas on what I'm missing here?

Thanks in advance.
Rob