Deleting an iPhone backup password

I changed the password on my iPhone backup. I want to back it up now, before the software upgrade, and I want to change the password again. The problem is, iTunes tells me that the current password is incorrect when I enter what I put down in my notes, so I can't change it. iTunes also will not make a new backup without encrypting it with the password which is unknown to me. I deleted all old backups and tried again, and I also tried making a backup without encryption. iTunes won't allow that without the password that I don't know. i do not want to have backups that use a password i don't know.

How do I get around this?