I'm using JGroups 2.2.9.1 with Java 1.5 on Ubuntu (linux 2.6.10-5-386) and i'm trying to run the demos QuoteClient and QuoteServer that is very similar to the application that i'll implement in our project with JGroups.
After launching 2 clients and 1 server and without doing anything the after a while the clients starts repeatedly throwing (full traces below):
2 [ERROR] TP.down(): - failed sending message
java.io.NotSerializableException: org.jgroups.protocols.pbcast.Digest$Entry
(...)

and hitting Get, Set or All buttons i get:
1355337 [ERROR] MethodCall.invoke(): - method getQuote not found
1365213 [ERROR] MethodCall.invoke(): - method setQuote not found
1366934 [ERROR] MethodCall.invoke(): - method printAllStocks not found

I'm concerned about the server behavior also because if there is no active client it is OK, but if there is one or more clients running the server gives a warning:
0 [WARN] STATE_TRANSFER.handleStateRsp(): - state received from 193.136.171.52:32771 is null, will return null state to application

I would like to know
1. if the 1st error is related with the warning from the server
2. why it seems to me that the servers closes after printing 'Ready to serve requests'? (i'm used to the rmi style)
3. why those methods aren't found?