unable to connect with OID

hi all,

i am using oracle application server 10g verison 10.1.2.3 i have enable recently enable SSO on forms leve; ssoMode=true when i run forms using this link http://hostname:7778/forms/frmservlet?config=claststsso

it show this error: 

500 Internal Server Error

oracle.forms.net.ConnectionException	
	
	at oracle.forms.servlet.FormsServlet.doRequest(Unknown Source)
	
	at oracle.forms.servlet.FormsServlet.doGet(Unknown Source)
	
	at javax.servlet.http.HttpServlet.service(HttpServlet.java(Compiled Code))
	
	at javax.servlet.http.HttpServlet.service(HttpServlet.java(Compiled Code))
	
	at com.evermind[Oracle Application Server Containers for J2EE 

10g (10.1.2.3.0)].server.http.ServletRequestDispatcher.invoke(ServletRequestDispatcher.

java(Compiled Code))