I used to get this problem a lot till i contacted dell adn got a replacement monitor, this morning though the problem happened again for the first time with this one. Just seems to be sometimes ill switch my pc on and the monitor refuses to display anything, ill have to mess around unpluging and reconnecting the dvi cable and turning the monitor on and off to get a display on it. I originally thought the cable was to blame, ive now 2 dvi and vga cables and the problem persists on them all. 
