Not sure this is related to any of the previous issues in the thread, but I had several Ubuntu 14.04 Fog servers using 1.2.0 that would unicast perfectly but get “starting to restore image” when multicasting.
I finally found that the FOG_UDPCAST_INTERFACE value under Multicast Settings was wrong. It was set to eth0 while my adapter was eth1. Not sure how I managed that, but hope it helps someone.