grub wont install during install procedure, image built onto usb by unetbootin, worked before then everytime i try to install from usb a second time it fails

[Neil Edwards]

when installing from usb the installer completes first time fine however when trying a second time from the same usb without rebuilding the image it wont work it says grub file is missing, rebuild using unetbootin and it all works fine....

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: ubiquity 2.15.26
ProcVersionSignature: Ubuntu 3.11.0-12.19-generic 3.11.3
Uname: Linux 3.11.0-12-generic x86_64
ApportVersion: 2.12.5-0ubuntu2
Architecture: amd64
CasperVersion: 1.336ubuntu1
Date: Fri Feb 21 23:09:28 2014
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz.efi file=/cdrom/preseed/ubuntu.seed boot=casper only-ubiquity quiet splash --
LiveMediaBuild: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
MarkForUpload: True
ProcEnviron:
 LANGUAGE=en_GB.UTF-8
 TERM=linux
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_GB.UTF-8
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.