Error - Cookies Disabled when deploy application at root


After create a Vaadin project (i.e. mysample) with Eclipse plugin, selece Tomcat 7.0 as target, and then add a button into mainWindow, the application (http://localhost:8080/mysample) can be accessed successfully.

Now change the deployment path to be root, the homepage (http://localhost/) can also be displayed correctly. But after click the button (actually any interaction), a meesage of “Cookies Disabled” is popped up (please see the attachment).

Check my browser setting - all cookies are allowed.

Did anyone meet the same error? or any additional setting?