To resolve the issue, rebuild the Logic Pro 9 Help cache.

1. Quit Logic Pro 9 and the Help if open.
2. In the Finder, choose Go > Go to Folder from the menu.
3. In the "Go to the folder" field, type the following (without quotation marks): "~/library/Caches/com.apple.helpd/Generated".
4. Click Go.
5. Remove the "com.apple.logic.pro.help" file from the Generated folder.
6. Restart the computer.
7. Wait a few moments for the cache to be rebuilt. The time may vary depending on the number of installed applications.
8. Open Logic Pro 9 and go to the Help menu.

When searching the help, the resulting topics should open as expected.