Hey Dave,
Could you go to host configurations - storage adapters and check what is the device "mpx.vmhba0:C0:T0"?
Or run esxcfg-scsidevs -l
Also were there any changes to the host in terms of BIOS/firmware/drivers/patch updates?
Also has a hardware diags been run? Could be a hardware issue with the "mpx.vmhba0:C0:T0" device for all we know
Thanks