Hello SL,
As I mentioned earlier, I upgraded the network drivers on my servers and I enabled HA back on the cluster. I haven't seen the error yet. Also the hosts are pinging perfectly fine after the driver update.
I would suggest you check the latest firmware for your server and drivers for your nic. Install them. That might resolve your issue. I too had not installed any driver. ESXi took it. Give it a shot.
Thanks,
AG