You don't need to full format. You wrote that you restored the backup and then rebooted. Did you wait a little while (at least three seconds) before you hit the reset keys? PFS3 has some kind of deferred write mechanism which only writes back the root block three seconds after the last access. This reduces the number of write operations to the root block but it also has the effect that changes are lost if you reset too early.
If it still freezes, you should boot without startup-sequence and run diskvalid and/or pfsdoctor on the partition.
