Hi
This is a minor bug. It is a result of a poor setup by a site admin but one where jDownloads could give a better error message.
The Single Category Menu item specifies a category. For present purposes assume menu item has Public view access.
If the specified Category has an access level of say Registered then the user gets a 404 error. This is not incorrect but 'unfriendly'. It would be better if jDownloads recognised this situation and gave a gentler message such as "Category is protected. Please contact your site administrator". jDownloads does handle this well in List All Categories by not listing those categories where the current user has no access.
The fault is of course a bad setup by the site admin but people might think the 404 error is a jDownloads fault.
Single Downloads does handle the situation with a "You are not authorised...." message.
Colin