There are widespread reports of problems with the latest version of QuickTime (QuickTime 7.7 on Leopard and QuickTime 7.6.6 build 1787 on Snow Leopard and Lion). This update is installed as part of Security Update 2011-006 for Snow Leopard and OS X 10.7.2 for Lion.
(The security update is the most likely culprit but it may alternatively have been caused by the iTunes 10.5 update that was released at the same time.)
The problems include:
Several people have been getting the message "An invalid public movie atom was found in the movie" when playing back in QuickTime Player. Final Cut Pro will either crash or display a white screen.
This seems to especially affect HDV files created by Focus Enhancements storage products. Focus has acknowledged the issue here (PDF).
The recommended solution is to downgrade QuickTime or restore an earlier version of your system from a backup or clone.
Matt Geller of Meta Media Creative came up with another way of solving the problem. Replace the following files with the versions from a computer without Security Update 2011-006 installed (or alternatively extract them using Pacifist):
Reboot your computer and the problem should be solved. Remember to make a backup of the files you replace, just in case.
Related forum threads:
Apple Discussions: Invalid public movie atom was found in movie
Apple Discussions: Help!!! Upgrading to iTunes 10.5 has destroyed all video in Final Cut Pro
Apple Discussions: Problems after QuickTime 7.7 update
DV Info: Public atom?
LAFCPUG: Invalid public movie atom was found in movie
Some people have had problems with Compressor, Cinema Tools, Final Cut Pro and QuickTime Player crashing at startup.
The crash log says:
Dyld Error Message:
Symbol not found: _ValidateAudioChannelLayout
Referenced from: /Library/QuickTime/QuickTimeComponents.component/Contents/MacOS/QuickTimeComponents
Expected in: /System/Library/Frameworks/QuickTime.framework/Versions/A/QuickTime
To fix this, copy /System/Library/QuickTime/QuickTimeComponents.component to ~/Library/QuickTime, overwriting the existing file in that location. Backup the file before you do this.
If you are using Lion, your user Library directory will be hidden by default. Use System Toolkit to make it visible.
Because of these issues, I would recommend steering clear of the latest security and iTunes updates on your editing machine, especially if you're using Focus Enhancements products. Anyone with this issue should notify Apple so they understand how widespread the problem is.