I have a similar situation!
I'm working on a huge project with about 90 materials and I was working during a long time, adding new materials with the interactive render, and I notice my CPU usage was 95%, so I save the project and tried to make a final render. And when I tried to render nothing happens, so I close the project, wait for a little and reopen it. Then I tried to render again and it was no materials in the render then I also notice there were no materials on Vray material list too!!!
So since I can see the materials on SketchUp, can I add them to Vray material list?
if not, I have an autosave project with the latest materials used, can I export all of them at once to my recent project?
I'm using:
SketchUp Pro 2016 (version 16.1.1449 64bit)
V-Ray 3.40.02
Windows 7 64Bit