Clustering doesn't work

Hello All, I config clustering for two tomcat using apache at front and mod_jk as connector. I tried a test application to check the configuration and it works fine. Session are being successfully replicated and failover is detected successfully. But when i tried this for my actual application, it does not work. I made the modification in httpd.conf accordingly and very carefully. There is no exception,no error in the logs. I am unable to track the problem. Initially i was getting NotSerializableException for a particular classes and i made them serializable. Now there is no exception but still i am unable to load the application if the hosting tomcat is shutted down even when the other tomcat member of the cluster are alive. Can you guys please help me. I can understand it is quite tough to produce the solution when you are not sure of the problem.

Thanks a lot.