Hi there DBA's

This is kinda urgent.
Can't connect to database.
get the folowing error:
ORA-12514: TNS:listener could not resolve SERVICE_NAME given in connect

1. I get a response when I do a TNSping to the DB
2. Can't connect to the same DB.

Checked TNSnames, sqlnet and listener.ora files?
Started / stopped Database and listener.
restarted box?

Nothing works.

Please Help!