[Plugin: People Lists] "Plugin does not have a valid header” Error

WordPress 3.0.1 at jmonkeyengine.org

I received the “Plugin does not have a valid header” error upon activation.

I found this tutorial, that seemed to fix it:
http://bumblesoft.com/how-to-fix-wordpress-plugin-does-not-have-a-valid-header-error.html

Changing the stable tag from “trunk” to “1.2” fixed it.