In this case "NoClassDefFound" is the second of two errors. The problem tries twice to start, in case something is resolved after the first attempt.
As a user the error does not say much, but can you open it again and paste the first of two errors please? The first one is more informative.
This looks like something failed to load Warcraft 3 ingame icons and hit a bug perhaps. But I wouldn't know more without the first of the two popups.