I get the same thing as well infortunately.... I even tried copying the other modelviewer.lua from the game directory just for kicks and giggles. I love using the model viewer to skin with, is there a version of the stand alone that does work well with windows 7? Then when I try and load a model into it I get all these shader error messages and a funky version of the model. The P-51D's prop is basically in a box and such. I'm pretty new to DCS so forgive my foolishness if it's something I'm doing wrong. I've tried several versions of the standalone model viewer now.
I was using the one in the main directory of the game and it worked like a champ until yesterday. It won't open now, I didn't change anything at all....guess it decided it had enough :doh:
EDIT: I think I found my issue. It was the usual culprit, a windows update that happened at least after FEB 12 2014 on my machine. Even the games model viewer works like it's supposed too now.