If you can see "a line item in the accounts list for them" then you should be able to click that line to select it and click delete to delete the account.
I am curious to know exactly what you are seeing in the Accounts & Privileges dialog. Perhaps you could post a screen shot?
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Tutorial-How to post a picture so that it shows up in your message
Good idea on the screen shot. Hopefully I attached it correctly. As you said, when selecting the accounts line item (as is shown in the screenshot) I SHOULD be able to edit or delete, but those functions do not work on those "blank" accounts. Nothing happens when I click them except a screen quiver - like it tried to do something. I cannot uncheck the "Active" checkbox, nor deactivate through a script as it says it doesn't exist, yet if I try to create a new account using the same account name it says it already exists. I can edit and delete any of the other accounts as normal.
Can't see any posted image, but from what you describe, I think your file is damaged. Recover the file and see what is reported by the recover process. I suspect you'll find the file has problems.