I am just starting out with Dart and ran into a little hiccup using Dartium that took me longer than it should have to realize what was going on.
Buried on the download page is this line:
The Dartium binary expires after 12 weeks.
And what that line doesn’t detail, is that Chromium will still launch, however, it will just silenty no longer execute Dart scripts.
To fix this, download the latest version of Dartium from the download link above.