You're using imgur, better to use other third hosting images e.g. imgbb, postingimages, or talkimg.
I think that what it is is that imgur added a new very restrictive per-IP limit on image downloads. So all ip.bitcointalk.org requests are blocked, but even many Tor exit nodes are being blocked, for example.
I'm not going to attempt to play some cat-and-mouse game with imgur, so people will just have to use a different service such as TalkImg.