Custom posts

My custom post type is apparently not using the custompostname-archive.php, custompostname-category.php and custompostname-single.php files that I have set up for them. They are instead (seemingly) using the primary (archive.php, category.php and archive.php) files.

I used the well-known “Custom Post UI” plugin to set up the one custom post type that I am using. I am relying on the plugin’s statement that any custom posts set up with the plugin will use the categories (my only taxonomy) established for the regular posts. However, when accessing these custom post categories in a category sidebar I’ve created with the standard WP widget, it calls the existing posts within that category.

I don’t know if I should hardcode anything into the functions template to make it work properly, as I don’t know if this will render the plugin code useless or make a mess.

Please help!