iMac external display setup issues

[kappiekaps]

Alright, I have a late 2009 iMac and have just recently purchased an LG 22" LED monitor (Model#E2242T) to extend my desktop. I have the apple mini display port to DVI adapter and a DVI-D dual link cable to connect my iMac to the monitor. The issue is that I cannot get a picture to show up on the external display. I can tell my desktop recognizes the external display because the screen turns blue for a short period and in system preferences I can detect the monitor and change its screen resolution. I have tried using a single link DVI-D cable and have tried changing the resolution because I understand it is limited. The external monitor does have a VGA input but I was trying to stick with the DVI cable because of the better image quality it offers and so I don't have to purchase another adapter. Any thoughts????