Hi all - I just opened up Logic for the first time in a while, and bad things were happening.
Here are a few of the details:
Create an audio track, set input to Input 1, output is Stereo Out
I am plugged into Input 1 and I can see input level both in Logic and on my interface
I record enable the track - I would expect to hear myself at this point, and I do not
I press record, and I play the guitar - I can see audio signal laying down on the track
Stop recording, and press Play - and I can hear the recorded audio
I did a little searching online, and found that in Settings > Audio > General, they mention a checkbox for "Input monitoring only for focused track, and only when input monitoring is enabled (as in Garageband)" - unchecking this resolved the issue. It seems that this setting has been toggled perhaps in 10.8.1? Or maybe something else changed it? I am 99.999% sure I didn't change it, and this has never been an issue before, so I wasn't even aware of this setting.
In any case, if you run into this, hopefully this is your solution. Phew.
Bob