This rare bug may be present in Logic X too but I only have Logic 9 so I wouldn't know. Under certain hardware combinations (in my case USB and Firewire MIDI devices at the same time) the ability to control Volume and Pan via Midi CC on an Audio Track is lost. This happens when an AUX-track is added to the Arrange Window. If an Aux-track is seleted in the Arrange Window and is controlled via Midi CC then when going back to a regular Audio Channel Midi CC can not control Volume and Pan anymore (this also goes for Fader Events to plugins). Workaround: To get out of this state select a Midi track. Send some Midi CC. Now select a regular Audio Tracks again and it can be controlled via Midi CC. Until an Aux track is selected again... My system: Mac Book Pro OS 10.8.5 Logic Pro 9.1.8 Midi USB: Evolution UC33, ESI MIDI Mate XT Midi Firewire: MOTU 823 mkIII If I switch off the MOTU-interface the bug goes away.