The reason you were getting those errors is probably because ufsrestore was trying to restore stuff to /proc or some other realtime OS specific directories which are constantly changing (like /dev/kmem and so on).

Not a good idea to overwrite system memory and process table entries while the system is up

You would have to either restore only what you need (use interactive ufsrestore) or just restore it to another filesystem other than root (e.g, another disk somewhere)