When I submit a Premium listing, I get a 404 page not found error message instead of an acknowledgement for the submission.
Answer:
You need to set up a URL where users are redirected when doing a premium submission. This could be a URL of your order processor (so that users can pay you for the submission) or just a normal HTML page on your web site thanking users for the submission if you are not going to charge for a premium submission.
You specify the URL where users are redirected to by going to the Control Panel >> Plugins >> Premium Link Manager >> Premium Link Settings