== Unplug ALL unnecessary hardware ==
That will eliminate the USB ports causing the KP.
''Startup single user mode ( hold down command-s after the boot boing ) and perform the /sbin/fsck command until it is clean''
# /sbin/fsck <- run this until it says volume appears okay''(no longer says "System modified)''
Will it start in target mode? Did you recently add/update any software? Are you running VMWare Beta? There was a "know issue with this".
Good Luck.
N.