I’m still running 10.4 on my MacBook Pro. This morning when I came into work there was a security update for Safari available which I duly installed. At this point it all went horribly wrong. Securityd swallowed 1.7GB of Ram (out of 2GB) and it caused my machine to page-in and out continuously.
The summary (I wasn’t brave enough to just rm the file)
sudo mv /var/db/CodeEquivalenceDatabase /var/db/CodeEquivalenceDatabase.org
and then reboot the machine.
Many thanks to the poster, you have, most definitely, saved my day!