I had the same issue with the shadows,you have to increase some values in V-ray(F 10 on keyboard)
Here is a comment let for me on a site :
I would suggest you to use sun light system,
Light cache multiplier should me lowered to lets say 0.7 some times i go even 0.07 :S
I believe that you are using an standard camera , from what i can see in the view port... Don't ! , Use the V-ray Camera , works better for me.
I hope this could help you !