Any static initializers in com.hrnexus.security.ThinUserProxy or in any class it needs to resolve when being initialized (e.g. type of a static field)? I've seen cases where a failure in a static initializer gets swallowed but the VM ends up treating the class as unavailable. The problem ends up manifesting itself as a CNFE. What the cache is doing in your stack trace is a basic deserialization operation using ObjectInputStream and the thread context classloader. Nothing particularly cache-specific about it. Another (vague) possibility is the exception somehow affects how jetty is setting the context class loader on request threads. If the TCCL isn't set to one that has visibility to com.hrnexus.security.ThinUserProxy you won't be able to deserialize. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4138448#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...