If you get an ORA-3113, why are you trying to connect again? If you have errors, send them as you see them (copy and paste the entire SQL*Plus contents).
[dann@dan-lap dann]$ oerr ora 24327 24327, 00000, "need explicit attach before authenticating a user" // *Cause: A server context must be initialized before creating a session. // *Action: Create and initialize a server handle.
Looks like you've got a serious configuration problem. Have you ever connected to this instance successfully? If so, what has changed since then? If not, then you should probably verify that your listener is set up properly and that your instance is up and the database open (check the alert.log).
This was first published in September 2004