Indeed; as you probably noticed, we were doing some infrastructure maintenance, which required us to take down the forum for a few days. Apologies for the downtime.
Excellent, good to hear that registration is working for you now.
I'm not sure about the BDNS API; it's not ours and we don't have any regular contact with whoever is running that service. Unless something has changed without my knowledge, OpenNIC no longer resolves Namecoin domains, because both Yegor Timoshenko (of PRISM Break) and I politely asked them to stop resolving Namecoin domains due to security concerns (kudos to OpenNIC for listening to Yegor's and my concerns and taking them seriously).
Generally I'd recommend resolving Namecoin domains via ncdns. It should be able to use your existing Electrum-NMC as a backend if you like.
The crash is a known bug; we have a patch sitting in our pull request list, but the patch isn't merged yet because I'd prefer to have a regression test for it. The reason the old registration still shows up in your wallet's Manage Names list is that, from Electrum-NMC's point of view, it looks exactly like some third party sent you a "name_new" transaction, which is something that you might want to be able to see (since you might be intending to complete the registration). If you want to get rid of the old registration in your Manage Names list, probably the easiest way is to create a new wallet file, and transfer your coins and your successful registration to the new wallet. Not ideal, and arguably it's problematic that some random person could send you a bunch of name_new outputs (though they'd have to pay the registration fee) and you wouldn't be able to clean them out of your wallet... not quite sure what the ideal UX is there. Happy to consider ideas for how this could be improved if you happen to have suggestions.