/ file system is full, but du does not show that it's full

[c0re]

# df -h
Filesystem     Size    Used   Avail Capacity  Mounted on
/dev/ad0s1a    496M    466M   -9.8M   102%    /

So it's full.

But by du it's not appeared to be full


# du -hxd 1 /
2.0K    /.snap
512B    /dev
2.0K    /tmp
2.0K    /usr
2.0K    /var
1.9M    /etc
2.0K    /cdrom
2.0K    /dist
1.0M    /bin
131M    /boot
 10M    /lib
356K    /libexec
2.0K    /media
 12K    /mnt
2.0K    /proc
7.2M    /rescue
296K    /root
4.7M    /sbin
4.0K    /lost+found
157M    /


I know that something (like running process) can hold file so it's
actually are not deleted. I rebooted server. But this not helped, so
it's not a process holding file.

Checked with fsck

# fsck /
** /dev/ad0s1a (NO WRITE)
** Last Mounted on /
** Root file system
** Phase 1 - Check Blocks and Sizes
** Phase 2 - Check Pathnames
** Phase 3 - Check Connectivity
** Phase 4 - Check Reference Counts
** Phase 5 - Check Cyl groups
47268 files, 238539 used, 15276 free (6684 frags, 1074 blocks, 2.6%
fragmentation)

No problems here.


# uname -a
FreeBSD host.domain.com 7.3-RELEASE-p4 FreeBSD 7.3-RELEASE-p4 #0: Tue
Dec 28 13:55:47 MSK 2010
root at host.domain.com:/usr/obj/usr/src/sys/MYKERNEL  i386

What's the problem here? Why df says that filesystem is full? Other
command may also say that can't write because file system is full.