Here's an imgur album that shows I have no private songs: http://imgur.com/a/O479x
Yet for some reason, even after deleting multiple tracks, it says I'm still over by 2 minutes. It's effectively bricked my account, and if I can't fix it, I'll probably just stop using Soundcloud.
Best answer by Mathis
Looks like no one has gotten back to you on this one yet. I've looked into your account details and you're all set to upload new tracks. When you delete something from your profile, our backend can sometimes take a moment until the deletion is fully processes. Hence, there might be a delay between you deleting tracks and your account showing that you've got x more minutes to upload after you had initially gone over quota.