I'm sure you have looked at this before but I thought I would mention it anyway. Can you connect to the database on the linux server from another machine? Can you connect to the database on the linux server from the Oracle management machine using sqlplus? Have you tried to ping the linux machine using the computer name? If you are trying to run the management server on windows, I'm not sure why you would look at the oratab file on the linux machine. Either the listener on the linux machine works or it doesn't. Just a few thoughts.