I had this same problem and couldn't find an answer online anywhere.
So I did a trial and error method!! Here is what eventually worked for
me.

1. Copy the file(s) that you are having the problem with and paste them
onto your desktop (into another folder if there are too many). DO NOT
COPY ANY TEMP FILES!

2. On the original folder - Right Click - Properties - Security.
Delete all names apart from yours (as an administrator). You may need
to uncheck the 'inheritable permissions' box at the bottom.

3. Delete the original folder that was holding the 'problem' file(s).

4. Create a new folder with the same name as the original folder that
held the 'problem' file(s) (it needs to have the same name in case
people have shortcuts to the folder).

5. Copy the file(s) that are on your desktop/held in the folder that
you created on your desktop.

6. Paste the files into the new folder that you created in step 4.

I have no idea what the initial problem was with the files, but doing
the procedure above worked for me!!

I hope this helps.

Cheers
Glenn