Echo Web Framework

when i deploy my war file on tomcat 6.0 it gives me following exception :-

Aug 3, 2009 4:02:26 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet SpeedSaleUIReportServlet threw exception
java.lang.ClassNotFoundException: nextapp.echo.webcontainer.LazyRenderContainer
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1387)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1233)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassL................

What is to be done , am i missing on something , .
When i run this web app thru Eclipse it runs only once untill some action event is fired , meaning when i run this application it loads a form , when i click on some button , the neccesary code is executed , but when i press some other button it gives me a message box when says something about server instance not found , any body has similar problem , please help me ..

Regards Vikram