Oracle returns an error ORA-01031: insufficient privileges Oracle returns an error "ORA-01031: insufficient privileges"
When I run sqlplus / as sysdba but sqlplus sys/oracle123 as sysdba doesn't, why? 


Oracle version: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit
Linux version: SUSE Linux Enterprise Server 11 (x86_64)


I know that Oracle uses OS authentication when running sqlplus / as sysdba, I also checked sqlnet.ora carefully and it contains SQLNET.AUTHENTICATION_SERVICES = (NTS). 

I also changed the oracle user's group, oracle user absolutely belongs to dba group because when I run command id the following information returns:

oracle@linux-mage:~&gt; id
uid=103(oracle) gid=106(dba) groups=105(oinstall),106(dba)


Another information is I can logged on through sqlplus sys/oracle123 as sysdba, but I can not shutdown the instance: 

oracle@linux-mage:~&gt; sqlplus sys/oracle123 as sysdba

SQL*Plus: Release 10.2.0.1.0 - Production on Mon Sep 5 16:29:57 2011

Copyright (c) 1982, 2005, Oracle.  All rights reserved.

Connected.
SQL&gt; shutdown immediate
ORA-24324: service handle not initialized
ORA-24323: value not allowed
ORA-27140: attach to post/wait facility failed
SQL&gt; shutdown abort
ORA-01031: insufficient privileges
SQL&gt;


i ran strace -o trace.out sqlplus "/ as sysdba" and get the following output message.
the strace message is too big. so i paste it into pastebin. please visit this link

http://pastebin.com/YpjVeG8u

ipcs -s and ipcs -ls information:
    oracle@linux-mage:~> ipcs -s

------ Semaphore Arrays --------
key        semid      owner      perms      nsems

oracle@linux-mage:~&gt; ipcs -ls

------ Semaphore Limits --------
max number of arrays = 200
max semaphores per array = 250
max semaphores system wide = 32000
max ops per semop call = 100
semaphore max value = 32767
Something must have gone wrong at the O/S level - check this page for some steps to track down the problem