500 Servlet Exception

java.lang.IllegalStateException: forward() not allowed after buffer has
committed.
	at com.caucho.server.webapp.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:144)
	at com.caucho.server.webapp.RequestDispatcherImpl.error(RequestDispatcherImpl.java:118)
	at com.caucho.server.webapp.ErrorPageManager.sendServletError(ErrorPageManager.java:334)
	at com.caucho.server.webapp.WebAppFilterChain.doFilter(WebAppFilterChain.java:167)
	at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:221)
	at com.caucho.server.hmux.HmuxRequest.handleRequest(HmuxRequest.java:392)
	at com.caucho.server.port.WorkerThread.run(WorkerThread.java:129)
	at java.lang.Thread.run(Thread.java:534)
Resin 3.0.3 (built Mon Sep 22 15:54:15 PDT 2003)