Windows XP time keeps slipping back an hour.

We have about 100 workstations in our office, and 20 or so of them are having this very annoying issue.

1. I have updated the BIOS to reflect the correct time.
2. All systems have the latest updates.
3. All systems have the latest DLST update
4. This started happening around when DLST went into effect. March 9th or after..
5. Being that someone will ask me to “simply replace the battery on 20 systems”, I did so on one. Still no change.
6. I did a net time /domain /set /yes and nothing happens.
7. Our domain controller has the correct time and time zone
8. I did a w32tm /resync and nothing happens.

Any ideas would be truly helpful.