Versions where the problem was observerd:
Virtualmin: 3.93.gpl or 3.94.gpl Webmin 1.590 Linux: Debian 6 (Kernel: 2.6.32-5-openvz-amd64)
The output of the following command, has more information:
# update-rc.d -f apache2 defaults
update-rc.d: using dependency based boot sequencing
insserv: warning: current start runlevel(s) (empty) of script `apache2' overwrites defaults (2 3 4 5).
insserv: script shinken.in: service shinken already provided!
This problem is not apache specific, it happens with every service we want to start automatically at boot time.