An LED monitor is an LCD monitor that uses LED for backlight. Aside form that, it's a regular LCD monitor. Check to make sure you are running at the native resolution for the monitor, and it may help if you list exactly what the error message is, and check the support site for the tuner card.
If I am reading this correctly your having a screen resolution issue with your LED monitor using a PC TV tuner card. Try adjusting the resolution. As for LCD and LED, that not entirely correct about just LED backlight.