du and df not in sync?

[Erik Steffl <steffl@bigfoot.com>]

  the du and df report quite a different amounts of data on my root
partition:

jojda:/home/erik# du -s -h -x /
110M    /

jojda:/home/erik# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/hda4             1.0G  649M  331M  67% /
/dev/hdb6             4.6G  1.3G  3.0G  30% /usr
/dev/hdb7              18G  9.4G  8.1G  54% /home
/dev/hdb2             6.5G  2.2G  3.9G  36% /mnt/old
/dev/hda1             786M  702M   84M  90% /mnt/win

  du reports 110M in / filesystem and df reports 649M used - that's
quite a difference. I have just ran apt-get clean (before that df
reported 97% used on /), is it possible that df does not use up to date
info? Is there anything I need to do before df reports current state
(which I think is 110M used)?

  I checked the man page and tried--sync as well but that gives the same
result.

  TIA

	erik