Vaadin 6.8 not working with Proxy


We are using a bit older version of vaadin i.e 6.8.10. Everything was working fine (without using service proxy).
But now when we are trying to render our gui page throught service proxy i.e there is a service proxy in between client and server, the panel opens up but with a Red colored vaadin box saying "
Session Expired

Can anyone help us understand the issue and any workaround for the same would be appreciated.