Hmmmm.......depending on which distribution you are running, have you tried going into the directory (e.g. /etc/rc3.d or whatever) and grep'ing everything for 'chage'??

I take your point that the log definitely seems to indicate that 'chage' is being run (at boot time) so I would try grep'ing for that.

Of course, something in rc3 could be calling something else which calling chage and that would need more detective work.