@Robert/Wlise
Can you see the device or partitions from the open firmware?
I forget the command now but you can ls the device and it should show the paritions and their respective FileSystems. If it's supported filesystem you can even list the contents of it.
ls /pci/ide/device@
,: maybe ?
0,0:0 for the first parition on primary ide channel, master drive afair
ls /pci/ide/device@0,0 should list the partitions
Entirely possible the MBR (Boot Sector) or RDB has become corrupted I guess, however, given that you get the MOS logo....safe to assume it finds the first FFS partition and the boot.img .. so I doubt it's an MBR problem.