You callback should explicitly be using android.view.MenuItem for context menu callbacks and not android.support.v4.view.MenuItem (which I'm going to assume is imported for normal options menu usage). If you add an @Override annotation to the callback you can ensure you're using the right type.
So I've experienced this in 2 separate applications. After adding adding ActionBarSherlock to the project and adding an action bar to the activity, the onContextItemSelected never gets fired when an item is clicked from a long press context menu. I've tried a bunch of different things from my various googlings, but nothing seems to work. Any thoughts?
ListView list = (ListView) findViewById(R.id.scroll_list);