How can I determine which App is Hijacking / Disabling my Option-Enter combo? I use Option-Enter A LOT. My main uses are to put a new line into a message in Messages, and to open a url in a new tab in Google Chrome, I know I can hit Command-T, but I often want to modify the url slightly and open in a new tab in one fell swoop.

This used to work fine all the time, now it will work for a while and then stop until the next reboot. I have looked at System Preferences->Keyboard->Shortcuts and there's nothing defined for Option-Enter.

If there is a likely culprit, please let me know. Otherwise, if you could explain how to determine which App or process is affecting this.

Running El Capitan 10.11.3
The problem was an extra keyboard that I had enabled: Unicode Hex Input. I had definitely forgotten about it. I would do something (not sure what, don't really care) to switch to this keyboard and when this keyboard is active the Option-Enter does not work.

I removed this keyboard from my list of Input Sources: System Preferences -> Keyboard, Input Sources Tab. Problem solved, no longer able to switch to this.

Below is a screenshot of my Keyboard Preference Pane on the Input Sources Tab.


Note: The oval is where the Unicode source was. When there are multiple sources the minus button (bottom left arrow) is active to remove the currently selected source. Also I have Show Input menu in menu bar checked - there will be no menu bar item if you have only one source.