I have Zimbra 8.04 (Open-Source version) running on a virtualized (KVM) instance of Ubuntu 12.04 LTS

I've installed everything appropriately and it was working fine, but after some period of time (which I haven't yet defined), Zimbra suddenly becomes inaccessible until I reboot the machine.
  • The strange part is that I can SSH into the machine fine so it's not a complete failure of the networking on the VM.
  • I've disabled the firewall and fail2ban and still can't access the machine
  • I've run zmcontrol and it shows all services as running fine

Rebooting the machine solves the issue but why?

My question is, why is Zimbra suddenly going dark?