VMware ESX 5.1 Question

So I've got this problem. Wonder if I can get any thoughts from you guys on wtf this may be. So I have an ESX server in a datacenter for some clients equipment. It runs some pretty vanilla stuff. Two of the VMs are sophos astaro security gateway v9's. Those two firewalls work flawlessly. Here's the problem I'm having. I spun up another server 2k8r2 vm specifically for the purpose of monitoring the environment. Nothing crazy on the vm. Installed my monitoring package. Same setup I use at 20 other sites. The only difference is the firewalls are virtual and the other sites have hardware firewalls. When I start the monitoring on the virtual machines it starts collecting data and locks up the whole esx environment and it turns to shit. The only way to stabilize is turn off my monitor vm and then reboot the firewall vms. Do you think that because I'm monitoring the system which contains the virtual firewalls that somehow I'm confusing it because the traffic is all passing inside one device? I can't figure this one out! It's like all the virtual disks in the san start acting in read only mode for the two sophos vms. Can't login to their web interface. They completely flake out.

Sophos support was pretty useless. They said they haven't run across a setup like this before. Maybe I'll get lucky and someone in here can throw some clarity at me!

-brad