So long story short, when I was creating the cache for the particles I evaluated Every .1, and saved every 10 to help with some stepping I was having with my particle system. When recreating the scene to recreate the problem I discovered that by evaluating every 1.0 and saving every 1.0 the issue is gone.

Apparently a cache that's evaluated ever .1 and saved every 10 (so still 1 cache file per frame) isn't something Vray DR likes?

Beats me, I've asked Vlado on the forums and will report here when I get an answer from him.