After a freeze of my Power Mac G5 (on MorphOS), I'm not able to boot it anymore. Here some informations:

- I can access to the Open Firmware with Cmd+Alt+O+F and the boot menu with Alt.
- But the boot process stay forever in a light grey screen (for MorphOS) or on Apple logo (for Mac OS X).
- If I disconnect the two hard drives, the machine show a question marks (?). I know it's a normal behaviour.
- If I insert the MorphOS CD and try to boot it, it go nowhere (grey screen).
- I copied the files of the MorphOS hard drive on another machine. All the partition and files were OK.
- I entered the Open Firmware to erase the nvram with the following commands:
reset-nvram
set-defaults
reset-all
...it was all ok but the "reset-all" command. It takes very long and the fans get crazy after 3-4 minutes so I shut up the machine (should I have waited for more?)
- Strange thing, after the first attempt to erase the nvram, I was able to boot Mac OS X once and only once. After less than one minute, Mac OS X diplayed a transparent black window indicating I must shut up the machine.
- Since then, others attempts to boot fails. No MorphOS, no Mac OS X.

Any idea?