ORA-12560: TNS:protocol adapter error
 *Cause: A generic protocol adapter error occurred.
 *Action: Check addresses used for proper protocol specification. Before
 reporting this error, look at the error stack and check for lower level
 transport errors. For further details, turn on tracing and reexecute the
 operation. Turn off tracing when the operation is complete.

c:\users\john\home>sqlplus jon/jon@rubbish

SQL*Plus: Release 11.2.0.3.0 Production on Mon Nov 28 20:28:00 2011

Copyright (c) 1982, 2011, Oracle.  All rights reserved.

ERROR:
ORA-12154: TNS:could not resolve the connect identifier specified


Enter user-name: jon/jon@orcl

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - Production
With the Partitioning, Oracle Label Security, OLAP, Data Mining,
Oracle Database Vault and Real Application Testing options

orcl> exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - Production
With the Partitioning, Oracle Label Security, OLAP, Data Mining,
Oracle Database Vault and Real Application Testing options

c:\users\john\home>tnsping orcl

TNS Ping Utility for 32-bit Windows: Version 11.2.0.3.0 - Production on 28-NOV-2011 20:28:52

Copyright (c) 1997, 2011, Oracle.  All rights reserved.

Used parameter files:
c:\app\john\product\11.2.0\dbhome_1\network\admin\sqlnet.ora


Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = jwdell.bplc.co.za)(PORT = 1521)) 
(CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = orcl)))
OK (20 msec)

c:\users\john\home>