Tabsheet: No UIProvider returned a UI for the request.

my UI contains a Tabsheet as top-most components. Initially, there is only one non-closable tab. Additional closable tabs are added dynamically when the user interacts with the first tab. This is working fine.
But after some minutes, when I switch between the tabs, I get following exception:

javax.servlet.ServletException: No UIProvider returned a UI for the request.
	at com.vaadin.server.VaadinServlet.service( [vaadin-server-7.0.3.jar:7.0.3]

	at com.vaadin.server.VaadinServlet.service( [vaadin-server-7.0.3.jar:7.0.3]

	at javax.servlet.http.HttpServlet.service( [servlet-api.jar:na]

	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter( [catalina.jar:7.0.37]


Under which curcumstances is this exception thrown? I am sure that the session is still alive, because I get a different error message when I wait much longer. I am using Tomcat 7 with its default settings, so the session timeout should have a reasonable value.

Kind regards, Seabstian

Even after deployment into a different application server, the problem still occured. So the problem was definitively on the Vaadin side.
Fortunately, I have found the cause. It was the HEARTBEAT which was not working. This caused that the Vaadin session became inactive and was removed. More information in thread!/thread/2043315