Ok so summary and explanations.
 
 * Reproducer:
  a) create two crontab files in /tmp
     /tmp/cron_a : * * * * * root /bin/date
     /tmp/cron_b : * * * * * root /bin/ls /tmp
     
  b) symlink cron_a to an intermediate symlink  
     % ln -s /tmp/cron_a /tmp/cron_symlink
     
  c) symlink this intermediate one to the cron.d directory
     % ln -s /tmp/cron_symlink /etc/cron.d/test
     
  d) Restart crond.
  e) Everything works as expected.
  f) Delete the intermediate symlink so we can add the other cron_b instead.
     % rm /tmp/cron_symlink
     
  g) symlink cron_b now to the intermediate
     % ln -s /tmp/cron_b /tmp/cron_symlink
     
  h) *DO NOT* restart just reload, nothing happens.
   
Ok vixie-cron is not well aware of symlinks, it doesn't know if we changed or
not a symbolic link; however everything is in place to reload stuff as the
signal is monitored and there is a sa_handler updating a volatile flag.

Now, the solution to this problem would be to just reload the database when
SIGHUP is send and/or, in other words, we did service crond reload. 
However, since the database is only checked when the modified time changed on
the directory /etc/cron.d, we miss the tick.. The solution then is to reset
m_time so we are sure this happens on SIGHUP.

This happens with all vixie-cron 4.1-xxx
Marcela, this also goes on FedoraCore and RHEL5, let me know if you want me to
clone the bug or you need anything else.

Also the patch has been tested succesful.

     Jose