GarageBand X - Sandbox Workaround for OS X Mavericks
GarageBand X in MAC OS X 10.9 Mavericks is now a sandboxed application and puts strong security restrictions on any AudioUnit plug-in loaded into a session.
To use S-GEAR v2 with GarageBand X, you must first run the S-GEAR standalone application (from your applications folder). Click on the S-GEAR 'i' button on the top bar in order to bring up the 'About' screen - this will ensure that the standalone application is disabled for audio processing. You can now load the S-GEAR plug-in in GarageBand.
This solution works because the S-Gear Application loads the license into memory, therefore the plug-in running in GarageBand doesn't need to.