On Jan. 15 Apple released an update to their widely used media wrapper Quicktime. In the last two weeks, reports have been pouring in all over the net about rendering issues with Adobe After Effects CS3, Mpeg 4 movies not playing, and Red media (from the RED ONE camera) having stability issues inside of Final Cut PRO.  Fxguide.com has an in depth article discussing the problem, and offers a handy solution involving third party software:

So you had a quick trigger and installed QuickTime 7.4 on OSX already…but there is no obvious way to downgrade. Are you stuck? No. Thankfully, the makers of the shareware application Pacifist have provided the tools to help you with this. The basic procedure is to1. Download and install Pacifist
2. Download the appropriate version of QuickTime from Apple’s web site
OS X 10.5.1 Leopard
OS X 10.4.11 Tiger
OS X 10.3.9 Panther
3. Make sure your system is updated to the version number listed for each 7.3.1 flavor of QuickTime.
4. Drag the QuickTime 7.3.1 package onto the Pacifist icon, or choose “Open Package” and open the QuickTime 7.3.1 download. Click “Install” and make sure you “Use Administrator Privileges”. When installing, make sure you replace files when asked.

You should be good to go.

The bottom line is if you’re in production don’t upgrade your box with every auto-update that comes through.