U60, DVD player, and hard drive

	Something on this show does not make sense to me: I was going to
upgrade the Solaris 10 version in my Ultra 60. So, I slap the DVD I
burned into the drive, boot the machine up, and tell it to boot off the
dvd just like I did it the last time. But the outcome is rather
different:

{0} ok boot cdrom
Boot device: /pci@1f,4000/scsi@3/disk@6,0:f  File and args: 

Can't open boot device

{0} 

Fine, I thought, so I tried to boot using the Solaris 10 DVD I used to
install the OS years ago. I had the very same outcome. Then, out of the
blue, I pulled out both hard drives and tried again. This time it
actually started fine:

{0} ok boot cdrom
Boot device: /pci@1f,4000/scsi@3/disk@6,0:f  File and args: 
SunOS Release 5.10 Version Generic_137137-09 64-bit
Copyright 1983-2008 Sun Microsystems, Inc.  All rights reserved.
Use is subject to license terms.
Configuring devices.
Using RPC Bootparams for network configuration information.
Attempting to configure interface qfe3...
NOTICE: SUNW,qfe3: No response from Ethernet network : Link Down - cable
proble?
Skipped interface qfe3
Attempting to configure interface qfe2...
NOTICE: SUNW,qfe2: No response from Ethernet network : Link Down - cable
proble?
NOTICE: SUNW,qfe2: No response from Ethernet network : Link Down - cable
proble?
Skipped interface qfe2
Attempting to configure interface qfe1...

Am I missing something here? To me, it does not make sense that the dvd
player gets annoyed when I slap one of the hard drives in the machine.
AFAIK, the hard drives and the CD/DVD/whatever are in two distinct scsi
chains.