Apple has released QuickTime version 4.1.2 in a stand-alone installer. The installer can be downloaded directly from Apple without having to go through an installer application. From Apple:
This stand-alone QuickTime 4.1.2 installer is for QuickTime 4 Pro users who need to reinstall their software. It does not require an Internet connection during initial installation. To update QuickTime to a future version, you can run the QuickTime Updater on the Internet or download a future version of this stand-alone installer.