When the replacement machines arrived we rebuilt the first computer and finished with the second. On the second we booted the 64 bit FC4 kernel successfully.
Early November the powersupply of the 64-bit kernel machine fried. A replacement was sent for and it exploded on contact with power. Meanwhile on about November 7, the 32 bit kernel machine stopped booting, probably bad power supply as well.
Referencing Directron's Power Supply Guide, we decided to throw the Diablo cases off the roof, and try an Antec Sonata II with a SmartPower2.0 450W power supply.