It appears to have crashed while booting up. What version of FreeNAS? What hardware? Has it ever worked? Have you changed anything since the last time it worked?
I've seen crashes like this when running from a USB stick that went bad or was corrupted.
A quick test would be to grab another USB stick, put a new copy of FreeNAS on it and try to boot from that and see what happens. If it boots fine, it's a pretty good indicator that the other USB stick is ready for the circular file.