vertical bars of maybe 2 cm width, every 6 or 7 cm, where the output is slightly blurred so that text is harder to read and is not sharp.
That's normal behaviour of flatscreen monitors with analog input, especially if you use it with different computers, for example through a KVM switch. Every computer and every gfx card outputs a slightly different signal. Use the auto-adjust button of your display to remove it. (Believe me, it has one. Check the manual.) You might have to repeat it when the gfx card becomes warm.
