I'm writing programs, so I need the pipe (vertical line) every now and then, but when I make the keyboard combination on my Azerty keyboard (i.e. option shift L), it launches iTunes and asks for a library. All other special characters can be made, except option shift M which also... launches iTunes (no ask for a library). All keyboard shortcuts are set to default (at least all that I found in Preferences), speech is off, virtual keyboard does not blink when I make the combinations.
We are completely in the dark, but I don't remember such a thing before iTunes 11, mountain lion and Tex Live 2012 (one of it may have caused it but that's just guessing).