Hi! Ok, In my case the FacesContext is null.
html.HtmlRendererUtils - *NULL* context null Servlet.service() for servlet opsj threw exception java.lang.NullPointerException at org.apache.myfaces.renderkit.html.HtmlRendererUtils.selectContentType(HtmlRendererUtils.java:1008) at org.apache.myfaces.component.html.util.AddResource.writeWithFullHeader(AddResource.java:713) at org.apache.myfaces.component.html.util.ExtensionsFilter.doFilter(ExtensionsFilter.java:139) It will be hard work to determine why the facesContext is null. One idea I have in mind is, that the given page has an iframe which will also be a faces page. Now that exactly this page works multiple times and only fails rarely I guess this has something to do with concurrency, though, the faces context is in an thread local, so why should this have something to do with conc? Odd, thing - If no one else has a new idea, I have to add more debug statements. --- Mario