Fix for "Unapproved caller. SecurityAgent may only be invoked by Apple software"

gistfile1.txt

- Start on single user mode: Hit the Command and S keys at start-up

Wait until the writing stops completely

-At the line, type (after root): /sbin/fsck -fy (space after the k)
Hit the ENTER key

wait until it finishes and says "... appears to be OK"

next, type: /sbin/mount -uw / (space after the t and after the w)
Hit the ENTER key

then type: rm -Rf /var/folders/* (space after the m and the f)

Hit the ENTER key

Run FSCK again (I did, just in case, but you may not have to):
/sbin/fsck -fy

Finally, type REBOOT, hit ENTER and wait until computer starts.