From MythTV Official Wiki
There exist cases where one graphics display system or another fails to show menus or video properly. These instructions are for forcing the frontend to use OpenGL for display.
- Start MythFrontend
- Choose Setup
- Choose Appearance
- Highlight Paint Engine
- Use the arrow to select OpenGL
- Choose the Next button. Keep choosing it until it turns into a Finish button. Select Finish and you are done.