ESX host drops out of communication

Ok this one is a little unusual.

Here are the symptoms that i've been seeing.

The host has had two losses of communication in the past 7 days.  One loss of communication was at about 7:30 pm and the other 4 days later at about 8:30 pm.  The environment has two ESX hosts and a vcenter server which is a physical machine.  The drop out has been on the same host, we'll call it ESX1 for simplicity's sake.

When i look at the logs for ESX1 i see a loss of communication with the iSCSI datastore which is hosted by SVSAN.  At the same time as the communication drop off occurs there is a spike in disk latency over 20000 ms that lasts until ESX1 is rebooted. When i first logged in to the vcenter server from the vsphere client i could see the machines on ESX1 but could not console into them, nor could i rdp into them.  I had the same results if i logged into the local host with the vsphere client.

I'm thinking this is a network issue but i'm not sure.  Its happened to the same host twice with the exact same symptoms.  There are no data recovery activities running at all and there doesnt appear to be any functions happening on the network at that time. I have pasted some of the event logs below to show what is happening.  Basically what is posted is repeated until the issue is resolved with a hard reboot of the host.

Any help diagnosing this would be appreciated.  Even if you can just point me in the right direction.

Thanks

GI