Try looking here for the log file:
/var/log/install.log
If you find it there please post it. A couple of possibilities that might be going awry are:
- You may have a file called PDFAdminSettings.plist that is failing to convert.
- Another possibility is that your "sudo" command is broken. To test this go to the Terminal app and type "sudo" without the quotes and hit the Enter/Return key.
sudo: can't open /private/etc/sudoers: Permission denied
sudo: no valid sudoers sources found, quitting
If you see the message above then you will need to contact Apple to help fix it.