I may be missing something, but is there a chance that the bios just doesn't wait long enough for the disk to turn on? On some laptops this sometimes happen to me when trying to boot an USB harddisk. The disk isn't detected at all by the bios, but generally rebooting with the disk already turned on fixes the issue. I've also seen an option on some BIOSes to wait for a few additional seconds at boot before enumerating drives, indicating that this may be a common issue.
Simon
