User prompted to upgrade off USB key as bootloader is installed

[Patrick Santos]

Prerequisites:
Have a copy of ubuntu-12.04-alternate-amd64.iso loaded somewhere accessible and a USB stick capable of accepting the aforementioned image.

Steps to reproduce:
1. Open Startup Disk Creator.
2. For the CD Drive / Image, select ubuntu-12.04-alternate-amd64.iso.
3. Select USB stick to load image on to.
4. Click "Erase Disk".
5. Confirm "YES" to the prompt "...erase the entire disk?".
6. Authorize formatting the device (by typing in your user password and clicking "Authenticate").
   6a. Wait for erase to complete.
7. Select the radio button "Discarded on shutdown, unless you save them elsewhere."
8. Click "Make Startup Disk" button.
9. Authorize installing the bootloader.

Expected result:
No upgrade dialog is shown until usb-creator has finished, or until the user unplugs the key and plugs it back in.

Actual result:
While the bootloader is still installing (the "Installing the bootloader..." loading bar is still open and active), a dialog box appears saying "Upgrade volume detected".

I reproduced this issue twice in a row, using unity 5.12-0ubuntu1 as my desktop environment. I also have a video (~2M file) showing my steps and the unexpected result.

-------------------------------------------------
Description: Ubuntu 12.04 LTS
Release: 12.04
usb-creator-gtk: Installed: 0.2.38
unity: Installed: 5.12-0ubuntu1

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: usb-creator-gtk 0.2.38
ProcVersionSignature: Ubuntu 3.2.0-24.37-generic 3.2.14
Uname: Linux 3.2.0-24-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.0.1-0ubuntu7
Architecture: amd64
Date: Fri May 11 23:16:26 2012
ExecutablePath: /usr/bin/usb-creator-gtk
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
InterpreterPath: /usr/bin/python2.7
ProcEnviron:
 LANGUAGE=en_CA:en
 PATH=(custom, no user)
 LANG=en_CA.UTF-8
 SHELL=/bin/bash
SourcePackage: usb-creator
UpgradeStatus: No upgrade log present (probably fresh install)

[Patrick Santos (milljudgement+ubuntu)]

Screenshot of "actual result" added:

[Launchpad Janitor (janitor)]

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