Archived - GarageBand: Multiple iControls may not work
If you're using an M-Audio iControl with GarageBand, the iControl may not work if you connect more than one iControl to the same computer.
If you connect more than one iControl to your computer, none of the control surfaces will work. Please note that GarageBand only supports one iControl device at a time. If you connect more than one, many buttons and controls on the first device won't work, and all additional iControls will be completely non-functional.