Google App Engine does not seem to support looking up directories from the servlet context path. This in turn means Click cannot find the templates to build up a cached map of templates to Page classes.
This problem only affects production and profile modes, not development modes, since development modes access the templates files directly (which GAE supports) if it fails to find it in the cached map.
The workaround for now is to manually map Pages to templates in the click.xml file:
<page path="home.htm" classname="HomePage" ></page>
<page path="/ajax/form-demo.htm" classname="ajax.FormDemo"></page>