Erase button is not enabled after an error occured during erase operation

How to reproduce:
1) Plug a USB flash to be erased and live image installed onto.
2) Select "Startup Disk Creator" in the Dash.
Case 1:
3) Select your flash to be erased in the list, click Erase button and then Yes.
4) When password prompt pops up, click Cancel.
Case 2:
3) Open terminal and `cd` to your flash mount point, so it cannot be immediately unmounted.
4) Select your flash to be erased in the list, click Erase button and then Yes.
5) Enter your password and press Authenticate button.

What happens:
Message box with an error information pops up (see attachments). After I click OK the Erase button stays gray and indicator stays spinning on it.

What is expected:
After Erase operation fail the UI should allow user to click on Erase button again if appropriate (I am not sure if every exception actually aborts the erase operation).
It would be good if a "human readable" explanation of the error such as "Cannot erase: not authorized" or "Cannot erase: the disk is busy" will be shown with details hidden by default.

Note:
This bug is reproducible on Ubuntu 14.04.1 as well.

ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: usb-creator-gtk 0.2.62
ProcVersionSignature: Ubuntu 3.16.0-14.20-generic 3.16.2
Uname: Linux 3.16.0-14-generic x86_64
ApportVersion: 2.14.7-0ubuntu2
Architecture: amd64
CurrentDesktop: Unity
Date: Tue Sep 16 16:45:36 2014
ExecutablePath: /usr/bin/usb-creator-gtk
InstallationDate: Installed on 2014-09-12 (3 days ago)
InstallationMedia: Ubuntu 14.10 "Utopic Unicorn" - Alpha amd64 (20140905)
InterpreterPath: /usr/bin/python3.4
SourcePackage: usb-creator
UDisksDump: Error: [Errno 2] No such file or directory: 'udisks'
UpgradeStatus: No upgrade log present (probably fresh install)