Do you still provide the service name in the tnsnames.ora file or SID. If it were SID then cheange it ti SERVICE_NAME and make sure it is the same as that of the SERVICE_NAME mentioned under initSID.ora file.

Next make sure that if you haven't removed the NAMES.DEFAULT_DOMAIN = world, you would want to comment that out, if you just want to use the jupiter as your connection string name. Hopefully this woud solve the problems ...

Sam