Android: getSupportActionBar() always returns null in ActionBarSherlock library
You should add the Sherlock theme to your application
<application android:icon="@drawable/icon" android:label="@string/app_name" android:debuggable="false" android:theme="@style/Theme.Sherlock">
I had the same problem on the Android ICS 4.0.4. I was using requestWindowFeature(Window.FEATURE_NO_TITLE); on the FragmentActivity, but this was hiding the ActionBar on ICS+ devices that caused the getSupportActionBar() to be null.
Simply removed the:requestWindowFeature(Window.FEATURE_NO_TITLE);
And it worked like a charm.
Hope it helps someone.
Another reason this will happen on Honeycomb+ devices is because the windowNoTitle attribute is set in your style. Get rid of that as ActionBarSherlock will automatically remove it in pre-Honeycomb devices for you.