Old Email Persists in iTunes

The original email address for my AppleID is obsolete. I have successfully updated to a valid address (and backup) on appleid.apple.com, and there is no sign of the old email address there.

However, whenever I initiate a purchase on iTunes on my MacBook, the AppleID prompt is the old address. I delete that and enter the correct (new) address and password, and I can complete the purchase. When I look at the Song Info/File page for a new download it shows the old email address for the AppleID. If I happen to enter the password without noticing that the email is wrong, login fails.

This doesn't happen with the App Store, where the new email is presented to me, and everything works fine.

It has been over a year since the change with many restarts and re-logins to iTunes, so it's not going to fix itself. It obviously isn't a huge problem, but it is irritating. How can I get that old address disassociated from iTunes on my Mac?

Thanks,

Dan