For some reason ntp isn't working properly on my office Mac, a
Quicksilver 867MHz running 10.2.6. The ntpd process is running and
/etc/ntp.conf has the content it should, based on the System
Preferences. Nonetheless, the clock consistently runs a little fast.
I can reset the clock manually from the ntp server via Set Time Now,
so the office Mac can definitely talk to the server. But it just
doesn't want to stay sync'd. I tried both a local ntp server as well
as Apple's (time.apple.com). The behavior is identical.

My Sawtooth 1GHz at home keeps consistently sync'd with time.apple.com.

What could be going wrong on the office machine? This is a real
headache with nfs file systems, which I use heavily. Fwiw I used to
run Yellow Dog linux on this hardware and ntp worked perfectly.