VelocityServlet : Error processing the template

com.msoft.common.exception.InvalidSessionException: Invalid Affiliate Session
com.msoft.common.exception.InvalidSessionException: Invalid Affiliate Session
	at com.msoft.affiliate.servlet.AffiliateSecureServlet.handleRequest(AffiliateSecureServlet.java:35)
	at org.apache.velocity.servlet.VelocityServlet.doRequest(VelocityServlet.java:372)
	at org.apache.velocity.servlet.VelocityServlet.doGet(VelocityServlet.java:333)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:114)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:91)
	at com.caucho.server.dispatch.ServletFilterChain.doFilter(ServletFilterChain.java:103)
	at com.caucho.server.webapp.WebAppFilterChain.doFilter(WebAppFilterChain.java:181)
	at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:266)
	at com.caucho.server.hmux.HmuxRequest.handleRequest(HmuxRequest.java:435)
	at com.caucho.server.port.TcpConnection.run(TcpConnection.java:603)
	at com.caucho.util.ThreadPool$Item.runTasks(ThreadPool.java:721)
	at com.caucho.util.ThreadPool$Item.run(ThreadPool.java:643)
	at java.lang.Thread.run(Thread.java:595)