Regarding the results: as you know the Internet is a very large sphere, and expanding and changing by the minute. We are and will never be always right, but our point is that we are able to show through the addons >90% of all green hosted domains.
In the case of Deviantart, it is hosted in the US by NTT. They might be using a CDN, that can theoretically fool the addon into thinking it is hosted somewhere else. We will look into it.
Using Firefox version 17, on LinuxMint 14 (Ubuntu 12.10) using the cinnamon desktop. It doesn't rely on Cache, Cookies, or offline website data for its positioning does it? Because for privacy I have firefox clear all that at close. None of the other extensions are effected by the clearing.