I came across some ‘problem’ with my MacBook a few weeks ago. After updating QuickTime, I wasn’t able to play videos with it anymore. What happens is that I only see a gray window, but the audio is being played. I don’t really know what caused it not to do so, but here are several suggestions short of reinstalling your whole system just to get it fixed:
- Try deleting 3rd party add-ins/plugins and reinstall them. There might have been a conflict between the latest QuickTime version and your existing add-ins.
- If QuickTime doesn’t play videos in Safari as well, delete QuickTime Plugin.plugin from /Library/Internet Plugins.
- Delete the plist file ~/Library/Preferences/com.apple.quicktime.plugin.preferences.plist — this will be re-created for QuickTime once it launches again.
- If all above fails, drag the QuickTime icon in the Applications folder to the Trash and install another in its place.