I did replace the LCD cable with a dual link cable, and the display works fine in 1600x900 mode in Ubutnu/Windows.
I built a Display Override for my panel, and now I can see the display in System Information under Graphics/Displays (a good sign!). However the display is still blank.
I'm wondering if it's coming down to a resolution issue with OSX that was mentioned above. Did any Macs ship with a 1600x900 screen?