Apple has revved its QuickTime software up to 4.0.3 yesterday. Although there is no public documentation regarding this update, this update probably stomps a few bugs in the QuickTime software. If you already have QuickTime 4.0.x installed, use the QuickTime Updater application to update to 4.0.3. Otherwise, there is no need to download the full installer unless you’re into that sort of thing.
