[Users] Data Center Non Responsive / Contending

Hi everyone, I'm asking for help again as testing my setup I put myself in a situation in which I can't get out. Layout: two hosts, an iSCSI storage, the engine installed as a "regular" KVM guest on another host (external to the oVirt setup). All CentOS 6.5, oVirt 3.4.0beta3. One DC ("Default"), one Cluster ("Default"), default storage type iSCSI. Moreover, ISO domain is another "external" KVM guest exposing an NFS share; Export Domain is in fact a VM in this Cluster. This is a preproduction setup. Yesterday all was running fine until I needed to do some hardware maintenance. So I decided to put the two hosts in maintenance from the webadmin then shutdown them in the usual way. Engine was left operational. Later i booted again one host, waited some time then tried to activate it (from the webadmin) without success. Even switching on the second host didn't change anything. Now the Data Center status toggles between "Contending" and "Non Responsive". None of the hosts is SPM and if I choose "Select as SPM" in the webadmin the result is this popup: ---------- Operation Canceled ---------- Error while executing action: Cannot force select SPM: Storage Domain cannot be accessed. -Please check that at least one Host is operational and Data Center state is up. ---------- The two hosts are operational but the DC isn't up (downpointing red arrow - "Non Responsive", hourglass - "Contending"). Storage domains are in "Unknown" state and if I try to "Activate" the Master Data Domain its status becomes "Locked" and then it fails with these events: . Invalid status on Data Center Default. Setting status to Non Responsive . Failed to activate Storage Domain dt02clu6070 (Data Center Default) by admin Connectivity seems OK. iSCSI connectivity seems OK. I'm almost certain that if I had left one host active I would have had zero problems. But I also think shutting down the full system should not be a problem. In the end I restarted the ovirt-engine service without results (as expected). Any thought? Logs needed? TIA, Giorgio.