What is your computer operating system? What is the video card/graphics card that your computer uses?
Assuming Windows 7, 8, 8.1, or 10 64 bit and that your computer is not using an Intel HD Graphics 2000 and higher video card/graphics card, please go to Edit Menu/Preferences/General. There please remove the check mark next to the preference "Use Hardware Acceleration (works on Intel HD Graphics 2000 and higher)". Look at the problem with and without this preference disabled.
Please let us know if that worked for you.
Any questions or need clarification on the above, please ask.