SQL & PL/SQL

Hi,
I wrote a procedure to be run before reinstalling a database. As I am not interested in rolling back, or waiting for transactions to finish, I am using SHUTDOWN ABORT to drop users. Everything works well in ORACLE 9i but it cannot restart in 10g - error:

ORA-12514: TNS:listener does not currently know of service requested in connect
descriptor.

The procedure looks like:

SHUTDOWN ABORT
STARTUP RESTRICT

declare
cursor cnt_usr is
Select username from dba_users where username in (....some user names);
str_cmd varchar2(400):='';
begin
FOR usr IN cnt_usr LOOP
BEGIN
str_cmd := 'DROP USER '|| usr.username || ' CASCADE ' ;
dbms_output.put_line ('Executing: '|| str_cmd);
EXECUTE IMMEDIATE str_cmd;
EXCEPTION
WHEN OTHERS THEN str_cmd := ' ';
END;
END LOOP;

end;
/
ALTER SYSTEM DISABLE RESTRICTED SESSION;
exit;

Any idea what may cause the error?
Thank you
Dan