Apple Software Update now lists QuickTime 7.3.1 and GarageBand 4.1.1. Looks like the QuickTime update fixes that nasty RTSP exploit that was demonstrated on Second Life. Update away!
QuickTime 7.3.1
QuickTime 7.3.1 addresses security issues.
This update is recommended for all QuickTime 7 users.
For detailed information on this update, please visit this website: http://docs.info.apple.com/article.html?artnum=61798
GarageBand 4.1.1
This update improves overall stability and addresses issues with file export to iPhone.