Probably an obvious thing, but just check to make sure that the quadlock connetor is sitting in the IQ unit 100%.
(From those pictures, it looks like the quadlock connector is not sitting fully inside the IQ unit).
This might explain why you got the screen to flash very briefly once, and the thing no longer works since.
(The caps would have discharged to flash the screen up very briefly, but without power going to the IQ unit, it would stop doing anything else pretty quickly).
From the looks of the wires you have used, it looks like only Rear speaker wires have been tapped in to.
(Though if any of those wires are shorted to ground anywhere, you may have problems)
Here is the correct wiring information for the IQ unit.
http://www.carmodder.com/view_doc.php?doc_id=72&model_id=90