Hi
Have a look to see if youve used any gif images in your textures. Sometimes this can be a hassle and cause issues.
The amount of times Ive had this particular bug is enough for me to look elsewhere for a rendering program! Absolutely shocking considering the price Ive paid for the product.
Look into the menue for vray within SU, it has an option there to force sydc all materials or something along those lines. Just try those also (avoid the first option whatever that is as itll force you to re apply all your textures).
Hope this helps and good luck!