Switch to the default aero theme and then do the following.

Click on the Start Button type in Services In the search box and then click on Services
Theme Changing Issue-1.png

Scroll down until you see unsigned themes select it in click on the Stop text and let it stop after that click on Start text and see if that works. Your screen may blink when you do this.
Theme Changing Issue-4.pngTheme Changing Issue-stop.png
Theme Changing Issue-5.pngTheme Changing Issue-start.png


Jerry