Oracle Metalink:
Error: ORA 6413
Text: Connection not open.
-------------------------------------------------------------------------------
Cause: Unable to establish connection.
Action: Use diagnostic procedures to ascertain exact problem.
There are a number of reasons why you'll see this error, the most common reason is that the TNS connect descriptor can't be parsed correctly.
To understand what is going on we need to understand what net does during connect. When net attempts to make a connect it will try and find out some basic information re the client configuration, it will make OS calls to find out which program is calling net, which user is currently logged on and the name of the PC. It bundles these up into the CONNECT_DATA to pass up to the server to propogate the V$SESSION views etc.
The problem comes if we start using brackets in the program name, username, or PC name.
To diagnose forget the TRC file get the LOG file and check for brackets in the connect_data.
Change the exe name, username or machine name to get around this issue.