hook_cron error?

[leon]

Hi all,

When I have 'cron.php' run by crontab, the system keep sending me this
email:
...
Warning: main(sites/default/settings.php): failed to open stream: No such
file or directory in /societies/cass/public_html/includes/bootstrap.inc on
line 642

Warning: main(): Failed opening 'sites/default/settings.php' for inclusion
(include_path='.:/usr/lib/php4:/usr/share/pear') in
/societies/cass/public_html/includes/bootstrap.inc on line 642
...

And the code under hook_cron isn't executed at all. Any ideas?
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