mail problem

Once I have an email address in the address book I can't seem to change it. I have written some names incorrectly, but when I correct them, they flip back to the incorrect version. Also every email a friend has ever used is in my machine somehow, and once they change email addresses the old ones also show up and I can't remember which is the new address without rechecking my address book each time. How can I delete old addresses that show up when I write an email and wrong addresses in the address book. I have tried deleting and rewriting but it still keeps returning to the old wrong item. Thanks

I don't know how you're trying to go about making changes right now, but this works for me... To correct address info, open Address Book from the Applications folder (or Dock if you have the icon there), select the contact to edit, click Edit at the bottom of the larger pane, make your changes and click on Edit again when finished to save changes.

What MYmacROX said. You probably also need to clear the "Previous Recipients" list in Mail (you'll find it under the "Window" menu).