It may be that your Nokia wants to encrypt your data to protect it, and need a new password. Just enter something, at least 12 characters long. Make sure that you remember that password.
It may be that the card already is password protected. In that case, you need to provide the actual password to use it.
If you just bough it from a store, return it and get a replacement under watranty.
If you bought from someone, ask that person for the password. If he can't give you the password, chances are that it's a stolen card.
You may try to format it when it's connected to a computer.