Processes that just won't die

["Michael Tang Helmeste" <glassfish@frogbox.dyndns.org>]

Is there any way (besides rebooting) to kill processes that just don't seem
to want to die?
I don't believe the process has any child threads or processes, but its not
responding to any type of kill signal:

sphere# ps auxww | grep ntp
root     29295  0.0  0.0   344     0 p0  RV     4:15PM    0:00.00 grep ntp
(csh)
root     23233  0.0  0.3   592  1700 ??  Ds    Sun10AM    0:00.01
/usr/bin/ntpd -p /var/run/ntpd.pid
root     26086  0.0  0.3   592  1700 ??  Ds    Sun08PM    0:00.00
/usr/bin/ntpd -p /var/run/ntpd.pid
sphere# kill -3 23233 26086
sphere# ps auxww | grep ntp
root     23233  0.0  0.3   592  1700 ??  Ds    Sun10AM    0:00.01
/usr/bin/ntpd -p /var/run/ntpd.pid
root     26086  0.0  0.3   592  1700 ??  Ds    Sun08PM    0:00.00
/usr/bin/ntpd -p /var/run/ntpd.pid
sphere# kill -11 23233 26086
sphere# ps auxww | grep ntp
root     23233  0.0  0.3   592  1700 ??  Ds    Sun10AM    0:00.01
/usr/bin/ntpd -p /var/run/ntpd.pid
root     26086  0.0  0.3   592  1700 ??  Ds    Sun08PM    0:00.00
/usr/bin/ntpd -p /var/run/ntpd.pid
sphere# kill -9 23233 26086
sphere# ps auxww | grep ntp
root     23233  0.0  0.3   592  1700 ??  Ds    Sun10AM    0:00.01
/usr/bin/ntpd -p /var/run/ntpd.pid
root     26086  0.0  0.3   592  1700 ??  Ds    Sun08PM    0:00.00
/usr/bin/ntpd -p /var/run/ntpd.pid
sphere# kill 23233
sphere# kill 26086
sphere# ps auxww | grep ntp
root     23233  0.0  0.3   592  1700 ??  Ds    Sun10AM    0:00.01
/usr/bin/ntpd -p /var/run/ntpd.pid
root     26086  0.0  0.3   592  1700 ??  Ds    Sun08PM    0:00.00
/usr/bin/ntpd -p /var/run/ntpd.pid


I've had this problem with other UNIX/type OS's before on different
machines, but I never could find out why.