It has come to my attention that if your photo's "server" number is 35 and you try to use the depreciated image URL format (i.e. "http://photos35.flickr.com/…." it will fail to resolve that server. You should use the new url format, which is:
http://static.flickr.com/{server-id}/{id}_{secret}_[mstb].jpg
If you're using phpFlickr::buildPhotoURL(), then you'll need to fix the format for that. […]