This issue occurs sometimes on some Windows 8 computers and is due to a small incompatibility with the Graphics drivers on the system.
If you are affected by this problem then you can try running the game in a Window.
To change to running in a window:
- Start the game.
- Click Options.
- Click to CLEAR the Full Screen option.
- Click the TICK button to save changes
The game will now run in a Window without flickering.