Fragment add or replace not working

The problem here is that you're mixing android.support.v4.app.Fragment and android.app.Fragment. You need to convert all uses to use the support library, which also means calling getSupportFragmentManager().

Something like this, for example:

    android.support.v4.app.FragmentManager fragmentManager = getSupportFragmentManager();
    android.support.v4.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    ExampleFragments fragment = new ExampleFragments();
    fragmentTransaction.replace(R.id.frag, fragment);
    fragmentTransaction.commit();

It is important to note that the support library Fragment and the normal Fragment are NOT interchangeable. They achieve the same purpose, but they cannot be replaced with one another in code.

Although this question may have been answered, it should be noted that the solution to overlapping fragments is to get the fragment ID (actually the FrameLayout id as declaring in your xml will lead to headaches) with a fresh "Fragment" instance:

FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
Fragment fragment = new ExampleFragments();
fragmentTransaction.replace(R.id.frag, fragment);
fragmentTransaction.commit();

I can't tell you how many hours I spent going through post after post with no solution. I read your other post that's linked in the comments above and I'm going to answer there as well just in case someone finds that first.

For those who are getting a ClassCastException, try this as well. You can have all the right libraries added, using FragmentActivity instead of Fragment, and have getActivity().getSupportFragmentManager in your code to stop errors in a ListFragment and you'll still run into problems with Fragments. Google docs don't show you everything, and Eclipse code completion will not always save you...sometimes you just have to fix the bug yourself!!