I am having the same problem, or at least very similar.
My computer suddenly went to blue screen in the middle of ordinary work.
PowerMac G4 2x867mHz,
2GB ram,
3 x 500 Gb internal HDs, (2 eSata, 1 ATA)
1 x 160 GB Internal HD, (ATA)
Mac OS 10.4.11 - software update used regularly - everything...