After installing some 3rd party software on Mac OS X, you may be asked to go into System Preferences, Security & Privacy, and click Allow. But when I tried this, clicking Allow did nothing.
Look for any running software that may be related to keyboard and mouse input. For example I had MagicPrefs running, which is an application that monitors and modifies mouse activity, so Apple was trying to protect the system by not allowing the button to be clicked.
After I quit MagicPrefs, I was able to click Allow, and then launch MagicPrefs again.