500 Internal Server Error

/buy/index.jsp:

javax.servlet.ServletException: Response has already been committed
java.lang.IllegalStateException: Response has already been committed
	at allaire.jrun.servlet.JRunResponse.resetContent(JRunResponse.java:170)
	at allaire.jrun.servlet.JRunResponse.sendRedirect(JRunResponse.java:648)
	at allaire.jrun.servlet.JRunResponse.sendRedirect(JRunResponse.java:641)
	at com.neodesic.web.servlet.HttpUtil.jumpToErrorPage(HttpUtil.java:60)
	at jrun__buy__index2ejspe._jspService(jrun__buy__index2ejspe.java:999)
	at allaire.jrun.jsp.HttpJSPServlet.service(HttpJSPServlet.java:40)
	at allaire.jrun.servlet.JRunSE.service(JRunSE.java:1013)
	at allaire.jrun.servlet.JRunSE.runServlet(JRunSE.java:925)
	at allaire.jrun.servlet.JRunNamedDispatcher.forward(JRunNamedDispatcher.java:34)
	at allaire.jrun.jsp.JSPServlet.service(JSPServlet.java:175)
	at allaire.jrun.servlet.JRunSE.service(JRunSE.java:1013)
	at allaire.jrun.servlet.JRunSE.runServlet(JRunSE.java:925)
	at allaire.jrun.servlet.JRunRequestDispatcher.forward(JRunRequestDispatcher.java:88)
	at allaire.jrun.servlet.JRunSE.service(JRunSE.java:1131)
	at allaire.jrun.servlet.JvmContext.dispatch(JvmContext.java:330)
	at allaire.jrun.jrpp.ProxyEndpoint.run(ProxyEndpoint.java:382)
	at allaire.jrun.ThreadPool.run(ThreadPool.java:272)
	at allaire.jrun.WorkerThread.run(WorkerThread.java:75)