Apple addresses some scary security issues in this latest update. If you have QuickTime on your system--and you do if you're using iTunes BTW--you might want to grab this. As of this morning, it wasn't showing up in that Apple Software Update application, but this link has a standalone installer:
About QuickTime 7.4.1 for Windows
QuickTime 7.4.1 addresses security issues and improves compatibility with third-party applications.
This release is recommended for all QuickTime 7 users.
QuickTime 7.4.1 for Windows SHA-1 Digest:
For explanation of what a SHA1 digest is, please visit this website: http://www.info.apple.com/kbnum/n75510
For detailed information on the security content of this update, please visit this website: http://www.info.apple.com/kbnum/n61798