listener errors

I'm trying to run a stored procedure from a client machine using SQL*PLUS. The stored procedure uses a C library to do some stuff and return a result, so I have an EXTPROC listener running. I've created a tnsnames.ora file on the client which identifies the TELEFAX database on the database server on LAB1. The moment I connect to the database using SQL*PLUS, I see the following errors in the listener log. Running TNSPING on the client shows that the network connectivity is fine, and that the listener is running. I wonder if there are any obvious oversights that I've made. The problem is that I can't run this particular stored procedure, although other normal sql queries against the same database run just fine.

Here are the errors reported by the listener:

NNC-00406: name "LISTENER_lab1" does not exist

NNC-00406: name "TELEFAX.ffu" does not exist

NNC-00406: name "PLSExtProc" does not exist

Here are the errors reported on the client running the stored proc:

ORA-28575 unable to open RPC connection to external procedure agent

ORA-12154: TNS:could not resolve service name Received on Fri Apr 11 2003 - 17:33:46 CDT