So I recently tried to compile a model for source and received a semi-cryptic error in the form of:
WARNING: *** Encountered VTF file with an invalid minor version!
WARNING: *** Encountered VTF file with an invalid full header!
I also had two materials on my model. The materials were in separate directories. I don't think either of those points were the problem. Considering it said the vtf file has issues I figured it was the vtf at fault. I had been using vtfedit to convert my png's to vtf's and I guess I hit a flag somewhere or something.
I fixed the problem by exporting my vtf from GIMP instead of converting it with vtfedit. I get the feeling I did something else too though. If that doesn't work for you, read on.