Hi,
There is other option through which you can unlock the user and also change the password:-
1. To unlock the user
goto SQL prompt, login using ora<SID>
$sqlplus "/ as sysdba"
SQL> update sapsr3.usr02 set uflag=0 where bname='username' and mandt='000';
2. To change the password to 19920706-
SQL> update sapsr3.usr02 set bcode='61D26428640DBAB5' where bname='DDIC' and mandt='000';
you are done and you can login now..
Krishna