Hi Philippe,
I have a problem with a virtualsite on my RAQ4. This site has a very big traffic per day and logfile are compressed every night, so webalizer could not analyse the web.log file. I think the problem comes from the logrotate configuration.
Check this one: http://list.cobalt.com/pipermail/cobalt-users/2000-July/016435.html It has been working great for me for several months now. Good luck... Nico