There's only one time you should publicly mention a domain name that you want... and that's after you own it!
That's probably not one that someone would be all over, but I've seen people post something like this on forums: "Which domain should I buy? Example.com or Example2.com? Both are available." Well, both were available, until that post.
Anyway, I'd guess it was/is a temporary glitch at DH's end, but if it's not quickly resolved, and the name is important to you, get it registered somewhere else and point the nameservers here. You can always transfer it here (after 60 days) if you want to use your free domain credit for it.
Save up to $96 at Dreamhost with ALMOST97 promo code (I get $1).
Or save $97 with THEFULL97.