Texture Animation broken in version 2.78? I'm trying to switch between two pictures during an animation and don't want to go to all the complexity of UV editing.  I found the following instruction which almost works in version 2.78, but not all the way?  Here's the link:
https://renderedsmoothie.wordpress.com/2013/10/07/keyframe-texture-change-in-blender-internal/

As you can see in the picture below, for the first half of the animation (screen shot on left), I've told texture to use the watermelon image.  The watermelon image shows up in the preview on the left, but the rendered view shows an apple as does the right picture in the texture preview.  

In the second half of the animation (screenshot on right), the texture editor knows that an apple is to be displayed as seen in the left picture of the texture preview.

Do I have a setting wrong?  Why would texture preview show two different pictures?  Is this method of animation broken in Blender version 2.78?  Is there a version of Blender that works with this very simple and easy method of changing a picture during an animation?

Thanks in advance for any help or advice.
You have keyframed the texture list not whether the texture is enabled. In the tutorial images you can see that the checkboxes turn yellow, not the entire list background.

It seems a small detail but the mouse needs to be right over the checkbox to the right when you press I so that only the checkbox gets the keyframe. You can also right click on the checkbox and select Insert Keyframe.