(Aspire ES1-512) can't remove hdd password

I set an HDD password a while ago, and while I haven't forgotten it, I can't remove it. I can change it to another password, but when I leave the new and confirm fields blank and hit f10, the change isn't saved and the previous hdd password remains. the hdd password is 'set' and the supervisor and user passwords are 'clear'.

Is there another way to clear the hdd password? I'm bios version v1.09.