Clock skew and time.mit.edu

[Ricardo Ramirez]

Hello,
I use kerberos primarily to send mail through MIT's servers. Commonly
I'll get a 'Clock skew too great' error. The stock answer for this is to
update your computer's clock with NTP to the world time servers. The
thing is, my clock is correct. It uses time.nist.gov or time.mit.edu to
set its clock. Plus, I check against time.gov to ensure accuracy. So why
does this error occur?
Also, I checked what the time servers were telling me by running the
command '/usr/sbin/ntpq -c rv navobs1.mit.edu time.mit.edu
time.nist.gov' right after I receive this error. I will sometimes see
time.mit.edu as much as 15 minutes off of the other two servers. I don't
understand the reason for such deviation. However, when the servers are
again synchronized, I still see the 'Clock skew too great' error. The
only way I can fix this is by running kinit. Is this a bug in the system
or am I missing something?
Thanks,
Ricardo Ramirez