RadeonX1900 XT and GeForce 7300: Does Not Go Together

Macfixit reports incompatibility issue when installing in a Mac Pro a GeForce 7300 and a Radeon X1900XT.
The problem is affecting Core Image that is not working on the Radeon whereas it is fine with the GeForce.
While waiting for a fix from Apple, the only way to get the best Core Image performance is to remove the nVidia GeForce 7300.