fsck is failing to clean a filesystem

[Paul Beard]

I have a FreeBSD 10 instance in a virtualbox that I just tried to reboot after a move and it is balking on loading /usr. Says no space in lost+found. I can mount it read only and it looks fine but mount -f fails. fsck -fy  just keeps returning the same message. The system was shutdown cleanly, I think, so not sure what’s amiss here. Can I salvage this or should I try to copy/image what I can and remake it?