Problem was solved after updating to build 3518.

NFS became "unstuck".

Probably normal, since it clobbered the whole previous system, just keeping the setup and configuration. Glad I didn't have to restore backups anyway.

Only problem is the NFS shares suddenly became prefixed with /shares/ and I had to unregister all the VMs on these shares, umount the shares, remount them with the new name and re-register the VMs.

Tedious at best...

The first boots with the new version took a very very long time, the web interface being unresponsive, even after everything was accessible again.

A final reboot gave me the web gui back.