2) Is it only in this project file? If it is, you could always try moving everything to a new project file. It would be real pain, but maybe your file is corrupt or something crazy.
Open a project and mysteriously one or two tracks would be hard panned left, always left, never right.
At first I thought it possible a MIDI message from my keyboard was being sent but later came to think it might have something to do with the Logic/Settings "Send Used Instrument MIDI Settings".