GRID GPU Crashing

Here is my setup:
Dell PowerEdge 630
(1) GRID K2
VMWare ESXi 5.5
Server is hosting (2) Windows 2008 VMs for XenApp

I setup the Card as passthrough in ESXi. I assigned (1) PCI GPU to Server A and the other PCI GPU to Server B

Server A is having no issues
Server B is seeing Video Freezes when users run programs that start using the GPU. I also see the same issue if I RDP into the VM and run GPU-Z.

In the Event viewer I get error entries for Display with the following. Display driver nvlddmkm stopped responding and has successfully recovered.

At first I thought it was a bad GRID Card - Dell sent me a new one, problem went away. 3 weeks later same problem retuned only on Server B. Now I’m thinking it’s not a hardware issue and something else. I built a brand new VM, shut down Server B and assigned it’s GPU to the new VM…problem followed

Anybody else ever see this? or better yet, anybody know how to resolve this?