Hello, I have a mid-2007 iMac 2.4 GHz (ATI HD 2600 Pro). I connected a (working, tested) Dell U2413 with (working, tested) DVI cables to my iMac using a mini-DVIDVI adaptor (not tested elsewhere, but with proper electrical continuity between respective pins). The iMac has never had any external monitor before. Mavericks detects correctly the monitor (model, resolution) and the monitor "feels" a computer connected, but I get only "powersave" in the monitor, nothing is displayed. Please note that "powersave" is not the same as "no signal". Both devices are detecting each other, but no image is arriving. Could you please help me? I have to quickly decide whether to return it of keep it. Thank you very much.