What is my disk usage?

[Janos Dohanics]

du is acting strange on my system:

# du /usr/X11R6
4       /usr/X11R6/share/locale
8       /usr/X11R6/share
12      /usr/X11R6

# du -h /usr/X11R6
2.0K    /usr/X11R6/share/locale
4.0K    /usr/X11R6/share
6.0K    /usr/X11R6

# du -k /usr/X11R6
2       /usr/X11R6/share/locale
4       /usr/X11R6/share
6       /usr/X11R6

This seems to be happening only after I have sudo'd myself. du reports
consistent numbers if I run it as myself or if I su first.

This is a  FreeBSD 6.2-STABLE system with snapshots enabled.

Any ideas?