[Users] VMs and volumes disappearing

Hi, I have recently set up an oVirt environment, I think in a pretty standard fashion, with engine 3.3 on one host, one oVirt host on a physical machine, both running CentOS 6.4, using NFS for all storage domains. Today I was playing around with snapshots, when I noticed that the Snapshots panel didn't show any of the snapshots I created, not even the 'Current - Active VM' snapshot that all VMs have. Not sure what to do, I decided to restart the ovirt-engine process. When I logged back on to the administrator panel, I was shocked to see 2 of my 4 VMs completely missing from the inventory. I haven't been able to find back a single trace of either machine, neither in the portal nor on disk. It seems like they never existed. The storage of both VMs seems to be erased from the data domain. A 3rd VM is down and refuses to start: "Exit message: Volume 337a410f-1598-4a7f-9afd-c0160c329563 is corrupted or missing." and in vdsm.log on the host: OSError: [Errno 2] No such file or directory: '/rhev/data-center/5849b030-626e-47cb-ad90-3ce782d831b3/d523a48d-7a34-4bb0-9d48-2092934af816/images/e803ad34-94e5-4180-b26f-7271bfca5923/337a410f-1598-4a7f-9afd-c0160c329563' So it seems something is seriously f*cked up. Now what? Any ideas what may have caused this? And more importantly, how do I prevent something like this from happening again? Perhaps a needless addition, but I am very scared to host anything remotely important on oVirt now. Regards, Martijn.