Dual displays on a Power Mac G5

A friend of mine has a DP 1.8 G5 tower with a dual head DVI card with two ADC 17" cinema displays connected to it using the DVI to ADC adapter. On one of the displays the color is inverted. All of the color settings are set correctly, and the display setting is set to the correct "Black on White" in universal access. It isn't an issue with the display since when you toggle the display setting to "White on Black" it just changes which of the two displays is the inverted one. Other monitors have been plugged into the machine with the same result. Likewise, it isn't an issue with the graphics cars as the card was recently upgraded and the problem with the inverted color persists.

This feels like a problem in software and not in the hardware, but perhaps the computer doesn't like having two displays plugged in with the adapter. Though we have tried other displays they have all been, shockingly, ADC displays. I plan on lugging over my 20" Aluminum soon to see if that works normally. I suspect that it will. Anyone have any ideas?