You have overriden newSessionStore() in your application in order to use HttpSessionStore rather than the default SecondLevelCacheSessionStore, haven't you? Take a look at Dan's blog entry : http://www.danwalmsley.com/2009/04/08/apache-wicket-on-google-app-engine-for-java/
cheers, /dd -- /* Spelin donut mader if iz ina coment */
