So it looks like Apple introduced security changes in the OSX 10.9 Mavericks. They removed the global option to allow apps (like PFixer) to control other apps (like Lightroom) and replaced it with a more finely grained, app-specific control mechanism. While it makes the OS more secure it means you have to make a fairly simple settings change after you upgrade to Mavericks.
- Open System Preferences
- Click on Security & Privacy
- Click the Privacy tab
- Select the Accessibility section from the list
- Click the "Lock" at the bottom and authenticate with OSX
- Check the box next to PFixer.app to allow PFixer to control Lightroom
- Close System Preferences
Restart PFixer and you should be good to go.