Ubuntu alternate installer fails when run from multi-boot usb device

[Tom]

When running a multi-boot usb drive and mounting ISO files to do installs, the ubuntu alternate(-i386) install cd fails. It will load and get part of the way (past the language/keyboard selection screens) then fails saying "Incorrect CD-ROM detcted". However, running the desktop(-i386) ISO from the same USB device works fine.

The multi-boot usb was setup similarly to: http://ubuntuforums.org/showthread.php?t=1288604

The grub.cfg file being used for both the good (desktop) and bad (alternate) boot images is attached to this.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: debian-installer (not installed)
ProcVersionSignature: Ubuntu 3.0.0-12.20-generic 3.0.4
Uname: Linux 3.0.0-12-generic x86_64
ApportVersion: 1.23-0ubuntu4
Architecture: amd64
CheckboxSubmission: 6de1b160d1e7e7ced8af1bd1a3901b47
CheckboxSystem: d00f84de8a555815fa1c4660280da308
Date: Fri Nov 11 21:32:16 2011
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Beta amd64 (20110901)
MachineType: Dell Inc. Dell System XPS L502X
MemoryUsage:
 total used free shared buffers cached
 Mem: 8107872 7929812 178060 0 111832 5612972
 -/+ buffers/cache: 2205008 5902864
 Swap: 7811068 0 7811068
ProcEnviron:
 LANGUAGE=
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.0.0-12-generic root=UUID=bbbbd628-e07b-40c1-9985-b3a60dfce333 ro quiet splash pcie_aspm=force i915.i915_enable_rc6=1 i915.i915_enable_fbc=1 i915.lvds_downclock=1 vt.handoff=7
SourcePackage: debian-installer
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 05/04/2011
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A05
dmi.board.name: 0YR8NN
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.chassis.version: 0.1
dmi.modalias: dmi:bvnDellInc.:bvrA05:bd05/04/2011:svnDellInc.:pnDellSystemXPSL502X:pvr:rvnDellInc.:rn0YR8NN:rvrA00:cvnDellInc.:ct8:cvr0.1:
dmi.product.name: Dell System XPS L502X
dmi.sys.vendor: Dell Inc.