Hi,
Okay when u try to shutdown the database through NORMAL option ,Oracle waits for the connected users to get disconnected.Till the users are not disconnected Oracle waits for the shutdown.Now in ur case shutdown abort works so the next time when Oracle starts up it performs instance recovery .What u do is that u do a shutdown abort of the database and startup and again shutdown in immediate option.
Try it out and it will work then on.....

In case of any help please be free to ask me at [email protected]

Regards,
Rohit Nirkhe,Oracle DBA,OCP 8i
[email protected]