The file manager or FTP should not be used if you're using Frontpage. Management of your files and directories should only be done through FrontPage. Using the File Manager to to set or remove permissions will corrupt your extensions, and your site will not work properly.
If you have files to delete, delete them through the
FrontPage Explorer.
You'll need to log in to the server live to do this.
Go to File/open web
Type in https://domainname.com
Type in userid and password in the dialog box
Give Frontpage a minute to do it's thing.
Go to folders view. You should see a listing of your website files with https://domainname.com at the top