I've just run into a rather strange bug. I put together a simple HelloWorld type portlet using Spring MVC portlet, and after deploying it, it shows up and is displayable. However, when I click on refresh, the following exception is thrown:

14:15:22,367 ERROR [[PortalServlet]] Servlet.service() for servlet PortalServlet threw exception
javax.servlet.ServletException: Unknown result org.jboss.portal.server.output.FragmentResult@19709b1
 at org.jboss.portal.core.servlet.CoreServlet.render(CoreServlet.java:223)
 at org.jboss.portal.server.servlet.AbstractMainServlet.invoke(AbstractMainServlet.java:81)
 at org.jboss.portal.server.servlet.AbstractMainServlet.doGet(AbstractMainServlet.java:71)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:697)
 ....

The strange thing is, that if I wait 30 seconds, and then click on reload, it displays properly. Anybody see anything similar to this? The same thing happens if I submit a simple form - if I don't wait 30 seconds after the initial loading of the page, the submit will also cause this exception. At this point I don't know if it's the spring code I'm using or if it's something nasty in the portal itself. In any case, the stack trace contains no references to spring classes.