It is having boot issues, won't turn on sometimes. Just keeps re-booting every few seconds. Finally got it going but wondering if there are too many cards and such ?
Keyspan serial card, Atto UL3D, Mix farm, Mix core, graphics card.
I would try a simpler setup. No Atto and no Farm to check if it is more stable. That means working with 2 ATA 66 <120GB drives(and a slow one on the ZIP bay). Anyway, with the 5 slots filled the machine sucks more from the PSU. If it is dying, will work worst with all the drive gaps filled+5 PCI.
Look at André setup and try a >450W PSU if you really need the 5 slots filled.
Apple PowerPC PSU were good but not the best. AcBel is tolerable, but Samsung on last MDD is really trash. Almost no Samsung PSU is alive. Most G3 and G4 have more life time than "newest" G5s, that is why it still worth giving new life to those studio machines with a new PSU if you can afford.
I am sure your set up without the ATTO and the FARM will work better with original PSU. If you upgrade the PSU you probably can work with the ATTO and the FARM also.