Oracle Database Discussions

Friends,

This strange problem is causing too much of trouble to understand.
Please help.

OS: AIX 5.3
Oracle DB: 9.2.0.8

When users are trying to connect to database server using the tnsnames alias with SID (below IWDEVSID) they are getting the following error.
ORA-01017: invalid username/password; logon denied. On consecutive attempts two or three time they get connected.

When they try to connect using the service_name, everything is OK like (IWDEV) below.
Whats wrong where.

There are not network delays. Setting up INBOUND_CONNECT_TIMEOUT_LISTENER = 0 on server side listener.ora doesnt help.

Client side tnsnames.ora
-------------------------------
IWDEV =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS =
(PROTOCOL = TCP)
(HOST = IWDEVDB)
(PORT = 1521)
)
)
(CONNECT_DATA =
(SERVICE_NAME = IWDEV)
)
)

IWDEVSID =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS =
(PROTOCOL = TCP)
(HOST = IWDEVDB)
(PORT = 1521)
)
)
(CONNECT_DATA =
(SID = IWDEV)
(SERVER = DEDICATED)
)
)

Client side sqlnet.ora is as follows
-------------------------------
SQLNET.AUTHENTICATION_SERVICES= (NTS)
NAMES.DIRECTORY_PATH= (TNSNAMES, EZCONNECT)


Server side listener.ora
-------------------------------
LISTENER =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = iwdevdb)(PORT = 1521))
)

SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(GLOBAL_DBNAME = iwdev)
(ORACLE_HOME = /uvxapps/oracle/product/9.2.0)
(SID_NAME = iwdev)
)
)


Server side sqlnet.ora
-------------------------------
NAMES.DIRECTORY_PATH= (TNSNAMES, ONAMES, HOSTNAME)



Kindly help me to understand what wrong here.

Thanks
Vishal V.