Security Update April 2002

requires Mac OS X 10.1.3 according to this Apple KBase article. It also contains this warning:

"You should not reinstall any earlier updates after using Security Update April 2002, including:

* Security Update 10-19-01
* Installer Update 1.0
* Mac OS X 10.0.x
* Mac OS X 10.1
* Mac OS X 10.1.1
* Mac OS X 10.1.2
* Mac OS X 10.1.3

Updates should be installed in the correct order. If for any reason you need to reinstall a software update prior to Security Update April 2002, the Mac OS X startup volume should be erased, after first backing up important documents and data. Reinstall Mac OS X, and install updates in the correct order."

[Dana Baggett]