I was struggling to find a WordPress function that made problems ... I just wasn't able to find the file where it was defined, so I made an OS X application to find that out. What the application does is scan through all files in the wordpress folder and than list all of them with all the functions/classes listed, this is the result for 1.5.3: http://www.osxcode.com/phpPackageScans/wordpress_packagescan.html
For OS X users, here's the app: http://www.osxcode.com/2005/11/28/php-package-scan-heres-the-app/
Should be quite useful for all plugin devs. :-)
Fredi