Dart Editor does not activate after upgrade - dart

Question

I upgraded Dart Editor today and now the Editor will not activate.
Instead I receive the following error in the "Tools Output" window:
"pub list-package-dirs failed: exit code 1"
None of the below actions has resolved this issue:
- Deleting and reinstalling Dart Editor and Dartium
- Running pub cache repair from command line,
- Manually deleting package cache directory and running pub get again.
I appreciate any advise on this.
My Dart Editor is version 1.8.3.release (STABLE)
Dart SDK version 1.8.3
Pubspec.yaml contents:
name: mpower
description: Sample app built with the polymer.dart package
environment:
sdk: '>=1.2.0 <2.0.0'
dependencies:
polymer: '>=0.15.1 <0.16.0'
dev_dependencies:
unittest: '>=0.10.0 <0.11.0'
transformers:
- polymer:
entry_points:
- web/index.html
Result of pub-list-package-dirs from Command Line:
{"packages":{"mpower":"C:\Users\jfontana\dart\mpower\lib","browser":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\browser-0.10.0+2\lib","matcher":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\matcher-0.10.1+1\lib","utf":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\utf-0.9.0+1\lib","source_span":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\source_span-1.0.0\lib","web_components":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\web_components-0.9.0\lib","string_scanner":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\string_scanner-0.1.2\lib","source_maps":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\source_maps-0.10.0\lib","mock":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\mock-0.10.0+1\lib","watcher":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\watcher-0.9.3\lib","args":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\args-0.12.1\lib","collection":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\collection-1.1.0\lib","barback":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\barback-0.15.0+1\lib","code_transformers":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\code_transformers-0.2.3+1\lib","csslib":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\csslib-0.11.0+2\lib","pool":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\pool-1.0.1\lib","polymer":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\polymer-0.15.1+3\lib","template_binding":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\template_binding-0.13.1\lib","smoke":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\smoke-0.2.1+1\lib","stack_trace":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\stack_trace-0.9.3+2\lib","html5lib":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\html5lib-0.12.0\lib","path":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\path-1.3.0\lib","observe":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\observe-0.12.1+1\lib","logging":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\logging-0.9.2\lib","yaml":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\yaml-2.0.1+1\lib","unittest":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\unittest-0.10.1+2\lib","analyzer":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\analyzer-0.22.4\lib","polymer_expressions":"C:\Users\jfontana\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\polymer_expressions-0.13.0\lib"},"input_files":["C:\Users\jfontana\dart\mpower\pubspec.lock","C:\Users\jfontana\dart\mpower\pubspec.yaml"]}
My OS is Windows 8.1
Java Version "1.8.0_25"
Java SE Runtime Environment (build 1.80_25-b18)
Java Hotspot 64-bit Server VM (build 25.25-b02, mixed mode)
Dart Editor version 1.8.3.release (STABLE)
Dart SDK version 1.8.3
I installed Dart by downloading darteditor-windows-x64.zip
and extracting contents into C:\Dart folder