is there a grub option to help my usb drive get recognized upon bootup?

[sarta53]

I'm using GRUB on a bootup CD that is intended to direct the computer to 
continue loading Ubuntu live USB from the attached USB thumbdrive on a Dell 
Lattitude C610 USB 1.1 port.  


I created a grub CD per directions at 
https://help.ubuntu.com/community/BootFromUSB#Booting%20the%20kernel%20from%20a%20bootable%20CD


The Linux kernel is included on the CD because this laptop is not capable of 
booting off the USB drive.

The GRUB boot CD and thumbdrive works on other computers but on this laptop I 
get the following errors:

ata2.0:  EH complete
ata2.0:  exception emask 0x0 Sact 0x0 sErr 0x0 action 0x6 frozen
ata2.0:  status { DRDY }
ata2.0:  link is slow to respond, please be patient (ready=0)
ata2.0:  device not ready (errno=16) forcing hard reset
ata2.0:  soft resetting link
ata2.0:  configured for P103
ata2.0:  EH complete
ata2.0:  limiting speed to P103

There may be subtle typos/omissions in these messages since I had to copy them 
by hand, but I hope this accurately communicates the problem.

My understanding is that after loading the linux kernel off CD, it's trying to 
continue by accessing the filesystem on the USB drive, which is not accessible.

The following bootstring was used:
kernel /boot/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper noprompt 
cdrom-detect/try-usb=true 


What grub options can I try in attempt to get the bootup process to access the 
filesystem on the USB drive at boot time?