I have the same issue with my addon and parked domains. I tried creating them a couple of times. I do sees them in my subdomain section dropdown but not in the addon and parked domain sections. I misspelled one of my addon domains and now I can't remove it. If I try to create it again the system tells me that the domain is already owned by another user. So to answer your question, I guess it's not fixed yet. can someone please help me with this.
My username is iceman18 and the domain I'm trying to add online-kleding.nu
Thanks in advance.