Looks like your profile's about section is null. I expected an empty string. In either case, you need to add the verification code to your profile and save it before you can verify your HN Notify account.
For what it's worth I had the code in there when I clicked verify and received the error. Glad to help with some error handling though :)
It has happened to a couple of people so far, seems like the API might have a little bit of a lag when updating a profile.
I haven't seen it first hand but what you and a couple others are see sounds like it might be the case. I'll keep an eye out.