Hosting subdomain

Assuming that I have registered and that I’m using DynDNS as my DNS provider, I would like to host the subdomain with DreamHost. However, when trying to add the subdomain using Manage Domains in the Web Admin Panel, I get this error message:

[color=#CC0000]Can’t add domain: you don’t have permission to add to[/color]

I have tried to add an NS record for pointing to (it seems like ns1 and ns2 are down right now), which should allow DreamHost to create the necessary A records in their DNS server, right? But to no avail.

What should I do? I do not want to use DreamHost’s DNS for the whole domain, since I need the dynamic features of DynDNS for other hosts in that domain, and I would prefer not to use ugly hacks like “cloaking”.

I did find this post from last year asking about the same thing, but I didn’t really see how to solve the problem in the replies. Do I need to contact support about this? It seems like a common thing to me.

Thanks in advance for any help!