Adding a host to HA

Hi!

have a simple setup: fresh 2 ESX 3.5 and a vCenter.

Want to make an HA cluster.

1. Create a cluster

2. Add a first host. OK

3. Try to add another.
        Error. "HA agent in cluster has an error"

I didn't put any licenses yet. The problem is not host-specific. If I try in reverse order, I get the same error on the 3rd stage.

/var/log/vmware/hostd-0.log:

Task Created : haTask-ha-host-vim.host.FirewallSystem.disableRuleset-6491
Task Completed : haTask-ha-host-vim.host.FirewallSystem.disableRuleset-6491
Activation : Invoke done on
Throw vmodl.fault.InvalidRequest
Result:
(vmodl.fault.InvalidRequest) {
dynamicType = <unset>,
msg = ""
}
Task Created : haTask-ha-host-vim.host.NetworkSystem.refresh-6493
Refreshing the entire network configuration...
Refreshed the entire ntwork configuration.
Task Completed : haTask-ha-host-vim.host.NetworkSystem.refresh-6493

Can anyone help, please?