I have a mid 2007 20" iMac. 2.4GHz Intel Core 2 Duo and ATI Radeon HD 2600 PRO with 256MB of GDDR3 memory. Current OS is 10.6.4 I've been trying lately to get a second monitor to work properly. I'm using a 20" Dell SP2009W. The second monitor (dell) randomly flashes black\off. As if it loses power or signal. It seems to be completely random. I tried the same monitor/cable/mini-dvi adapter with my MacBook. It works 100%, on all resolutions. Also running bootcamp with XP, XP and the second monitor work 100%. Never had any issues, only on the mac side. I do not believe there is any issues with the monitor or cable. I though it could be my video card or dvi port. But, it seems to work fine while booted in Windows. I've tried all the updates I could find, it is very annoying not usable at all. Any tips or suggestions?