I was unable to access Vaadin's Visual Editor in Windows 8.1 & Eclipse Kepler 64bit. Gettiog all kinds of errors. Following is how I've solved the issue.

Add following line to eclipse.ini solved the problem:

-Dorg.eclipse.swt.browser.XULRunnerPath=C:\

Note: You don't need to have XULRunner actually installed for this solution to work.

Once you open your Eclipse, right click on Vaadin Composite (*.java) and go to Open With, then select Vaadin Editor. You'll be presented with a following error:

Just select: "Do not show this message in the future" and you'll be fine.

Note: Vaadin example (sample) project doesn't by default include Vaadin composite java file. This basically means, that sample file by itself is not supporting Visual Editor, unless you add a Vaadin composite file to it. In any case, you can add one by right clicking your example class and select: New / Vaadin Composite.