My guess is that they are not being deleted at all, and that there is some kind of permissions issue.
To confirm this, please go to the FAQ (link) below) and read the topic 'Getting to know Eraser6' which tells you how to read the task log. Then open the Eraser window, and see if a task (or more than one) related to the failed erase appears there. If it does, read the log. If not, try erasing again, and see what the log says this time.
Now run Eraser as Administrator (instructions for doing this are in the FAQ topic), and see if the offending files are erased. If they are not, please tell us what the logs say.