ORA-01092: ORACLE instance terminated

I installed Oracle 10g R2 (10.2.0.1) base on SUSE 11SP3 and created the database.
Then i wanted to patch the database to 10.2.0.5
I show down the Listener and Instance and Applied the patch (10.2.0.5).
Then i started the Instance.It suddenly terminate the instace. By Giving
ORA-01092: ORACLE instance terminated.Disconnection forced
Error:
SQL> startup
ORACLE instance started.

Total System Global Area  599785472 bytes
Fixed Size                  2098112 bytes
Variable Size             213912640 bytes
Database Buffers          377487360 bytes
Redo Buffers                6287360 bytes
Database mounted.
ORA-01092: ORACLE instance terminated. Disconnection forced.

I carried out following steps and those saved my day...!

cd $ORACLE_HOME/rdbms/admin
sqlplus "/as sysdba"
SQL>startup upgrade;
SQL>@catupgrd.sql
SQL>shutdown immediate;
SQL>startup;
SQL>@utlrp.sql



cheers :)