If you use VGA or DVI-to-VGA with high resolution, it could be a moire issue, but I saw this only on CRT screens. I don´t know if this is a TFT issue too. Well, look into the settings of your display, maybe a "moire correction" option is available and fix it.
However, it could also be a scaling problem from the display. Try to use the native resolution of the display, i.e. the native resolution is 1600x1200 and you running 1280x1024 you may - as you do - see a blurry screen.