Hi Abhaysk,

Please post ur Listener.ora,SQLnet.ora & TNSnames.ora.
Listener.ora
----------------
PROD =
(ADDRESS_LIST =
(ADDRESS= (PROTOCOL= IPC)(KEY= EXTPROCPROD))
(ADDRESS= (PROTOCOL= TCP)(Host= xyz)(Port= 1521))
)

SID_LIST_PROD =
(SID_LIST =
(SID_DESC =
(GLOBAL_DBNAME= PROD)
(ORACLE_HOME= f:\oa\proddb\8.1.7)
(SID_NAME = PROD)
)
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = f:\oa\proddb\8.1.7)
(PROGRAM = extproc)
)
)

STARTUP_WAIT_TIME_PROD = 0
CONNECT_TIMEOUT_PROD = 10
#TRACE_LEVEL_PROD = OFF

trace_level_PROD=16
LOG_DIRECTORY_PROD = f:\oa\proddb\8.1.7\network\admin
LOG_FILE_PROD = PROD
TRACE_DIRECTORY_PROD = f:\oa\proddb\8.1.7\network\admin
TRACE_FILE_PROD = PROD

SQLNET.ORA
--------------
SQLNET.AUTHENTICATION_SERVICES= (NTS)
NAMES.DIRECTORY_PATH=(TNSNAMES, ONAMES, HOSTNAME)

TNSNAMES.ORA
----------------
PROD = (DESCRIPTION=
(ADDRESS=(PROTOCOL=tcp)(HOST=xyz)(PORT=1521))
(CONNECT_DATA=(SID=PROD))
)

#
# Intermedia
#
extproc_connection_data =
(DESCRIPTION=
(ADDRESS_LIST =
(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROCPROD))
)
(CONNECT_DATA=
(SID=PLSExtProc)
(PRESENTATION = RO)
) )


In case if u are using authentication as
SQLNET.AUTHENTICATION_SERVICES= (NTS)
Then u need to check in the USER Groups ORA_DBA that the current NT loginID is added in it.
I checked and it is there in the user group ORA_DBA.

If u r not using NTS authentication then the Pswd u r giving is wrong or might have been changed due upgrade.......am not sure...
We do use NTS Authentication and password is correct.

If I start the database listener and 'OracleServicePROD' service first and then start the database, I do not get any error messages but in my prev. version, I used to start the database directly thru SQL*PLUS without even starting the listener and 'OracleServicePROD' service.

Thanks,