I uploaded a new track that I didn't want to appear on my profile - I just wanted to send it to a few people.
I set it to private, and then requested a secret link. The secret link works when I log in to soundcloud, but if I am logged out, I get the 'sorry! we can't find this track' page. I am definitely using the correct secret link. Incredibly frustrating as I put the link up on the band facebook page, then found out it wasn't working and had to delete it.