Yes, the OracleSERVICEDBNAME is not the same as the ORACLETNSLISTENER, and the only way you can run a database is to have this running for each instance.

Do you get any errors in the NT Event viewer?

Do you just have the one instance? If not, do others start ok?

You could always use the ORADIM utility to delete and recreate this service and see if that helps.

Terry