CPT ERR: cc4c0800,28000 :Unknown image version: 304. Can't restore.

This happens when you live migrate between OpenVZ servers with different kernels running, at least significantly different by date.

There is no solution except to make sure you're running the same kernels on all machines, or at least not kernels that are much older or different (this is just a guess though, you should ensure all kernels are the same).