Apple has released MainStage 2.1.1 (http://www.apple.com/logicstudio/mainstage/), an update of the live performance application that turns the Mac into a streamlined live rig. It’s part of the Logic Studio suite.
This update resolves several issues, among them stability fixes for 32-bit Audio Unit Bridge plug-ins. MainStage 2.1 requires Mac OS X 10.5.7 or later. Logic Studio Pro costs US$499.