ORA-12641: Authentication service failed to initialize

test@linux1:~>sqlplus test/test@testdb

SQL*Plus: Release 10.2.0.1.0 - Production on Mon Jun 1 17:05:04 2009

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ERROR:
ORA-12641: Authentication service failed to initialize

Solution:
Step 1: check sqlnet.ora ($ORACLE_HOME/network/admin/sqlnet.ora) file
Step 2: Check SQLNET.AUTHENTICATION_SERVICES value
Step3: If SQLNET.AUTHENTICATION_SERVICES value is ALL (i.e. SQLNET.AUTHENTICATION_SERVICES=(ALL))
Step 4: Set the value for SQLNET.AUTHENTICATION_SERVICES is NONE (i.e. SQLNET.AUTHENTICATION_SERVICES=(NONE))