[pipcleo]

It seems 1.7 materials not backward compatible with 1.6.
Cant open a 1.7 mat in the 1.6 material browser.

several latest mats in the library will not open in the 1.6 material browser

[Mihnea Balta]

No, of course not. Most software provides backwards compatibility, i.e. a file created with version X will open in version X+1, but providing "forward compatibility" is hard or even impossible. Try opening a Max 9 scene in Max 8, or a Maya 2008 scene in Maya 8 and so on and you'll see it's not possible.