Remove the card from the phone and plug-it to a computer using a card reader then try to access the files. It has been reported that this trick works in some cases. Additionally, you will need to visit the Nokia Store because this will require the help of a Nokia technician. If you don't want to visit Nokia Store then there is always the possibility to obtain help from a local phone service shop. They should be able to remove the password.
Note: During this operation, the content of the card might be lost.