Ended up contacting my server support and they fixed it. Wish I knew how…
I had the same problem on my virtual private server. Finally gave up and submitted a support ticket. Wish I knew what they did – but whatever it was, it worked.
So I found http://ww.wp.xz.cn/support/topic/using-acl-to-give-write-permission-to-uploads-directory?replies=3
And gave it to my hosting provider support. Usually they get back to me within the hour (if not within minutes)…
After giving them that link, they’ve been silent for like 3 hours now. Stumped ’em?
Someone has to know how to manage ACL for this issue.