This VRay release was released recently (for Max 2013, i mean) and is not supported in Forest.
Really i didn't realize until now of this issue, so i was trying to compile the VRay DLL for you. Unfortunately there are some missing files in the installation package, that we need for compiling.
I just write a post in the ChaosGroup site. I will send you a custom build, as soon as we got the required files.