One could have an Oracle installation (10g, in my case) on a Windows XP machine). To bypass the problem of connection loss you could set SQLNET.AUTHENTICATION_SERVICES to none but then sqlplus / as sysdba won’t work anymore (obviously).
So I set my SQLNET.AUTHENTICATION_SERVICES back to NTS (using TNSNAMES)
The problem of connection loss doesn’t seem to appear anymore, maybe it’s because of a correct network binding (listener)?
NAMES.DIRECTORY_PATH= (TNSNAMES, EZCONNECT)