Disk space

Has anyone else experienced any unusual drops in available disk space lately? Over the past two days, I have lost approximately 175MB in available disk space according to the df reports, but the du reports show no significant changes in disk usage (maybe 200KB). Below is an example of the problems I'm encountering, over only a period of four hours.

At 9:00am this morning:

root@whiskey:~# df -h

Filesystem Size Used Avail Use% Mounted on

/dev/ubda 1.5G 789M 639M 56% /

root@whiskey:~# du -sh /*

6.0M /bin

0 /cardfound

232k /dev

2.4M /etc

17M /home

14M /lib

1.0k /lost+found

4.0k /mnt

0 /proc

388k /root

5.6M /sbin

5.0k /tmp

364M /usr

6.5M /var

root@whiskey:~#

…

Four hours later:

root@whiskey:~# df -h

Filesystem Size Used Avail Use% Mounted on

/dev/ubda 1.5G 800M 626M 57% /

root@whiskey:~# du -sh /*

6.0M /bin

0 /cardfound

232k /dev

2.4M /etc

17M /home

14M /lib

1.0k /lost+found

4.0k /mnt

0 /proc

388k /root

5.6M /sbin

5.0k /tmp

364M /usr

6.5M /var

root@whiskey:~#

As you can see, there is no change in the du report, but a 13MB change in the df report.