Any idea what the web server software is? For instance, Apache uses .htaccess files, but IIS doesn't.
Clearly the problem with not being able to browse the directory is due to a setting. These things are set in .htaccess files if you're using Apache. Do you have access to the directory either directly or via FTP? If you do, you can check the file to see if it disallows directory browsing (It will say Options -Indexes somewhere in the file).
As for being unable to upload to the directory, You need to do the following:
If the directory you're trying to upload to is ERP\SuperSecret\GilloD\, and you have 777 permissions on GilloD, check the status on SuperSecret to verify that you have proper permissions there. If you don't have permissions to upload to the parent directory, you'll never be able to upload to he directory you're trying to get to.