And what are its usual causes.?

I took the default Seam Web Project created by Red Hat Developer Studio and created a war file using the export selection on the drop down. I put the war in default/deploy in the jboss supplied with the Studio. When I open a web page to the application context in localhost:8080, I get the following

An Error Occurred:
No active application context
+- Stack Trace

java.lang.IllegalStateException: No active application context
at org.jboss.seam.core.Pages.instance(Pages.java:437)
at org.jboss.seam.ui.HtmlLink.encodeBegin(HtmlLink.java:105)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:884)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:892)
at com.sun.facelets.FaceletViewHandler.renderView(FaceletViewHandler.java:571)
at org.ajax4jsf.framework.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:101)
at org.ajax4jsf.framework.ajax.AjaxViewHandler.renderView(AjaxViewHandler.java:221)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:106)
at com.sun.faces.lifecycle.LifecycleImpl.phase(LifecycleImpl.java:251)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:144)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:245)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.jboss.seam.web.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:63)
at org.jboss.seam.web.RedirectFilter.doFilter(RedirectFilter.java:45)
at org.jboss.seam.web.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:49)
at org.jboss.seam.web.ExceptionFilter.doFilter(ExceptionFilter.java:57)
at org.jboss.seam.web.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:49)
at org.jboss.seam.web.MultipartFilter.doFilter(MultipartFilter.java:79)
at org.jboss.seam.web.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:49)
at org.jboss.seam.web.SeamFilter.doFilter(SeamFilter.java:84)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.ajax4jsf.framework.ajax.xmlfilter.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:75)
at org.ajax4jsf.framework.ajax.xmlfilter.BaseFilter.doFilter(BaseFilter.java:213)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:179)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:433)
at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:157)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:241)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:580)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Unknown Source)


When I look in default/log/server.log, there are actually three errors in a row:
no active event context
no active application scope
no active application context

The only addition to the generated code is the addition of a datasource -- which is not being used in the generated code.