有效的JSON，但来自AFNetworking / NSJSONSerialization的'Cocoa error 3840'

I've been hacking away for hours trying to solve this problem to no avail - it seems like my only option is to post here to see if anyone can shed some light on this issue. It may be an issue with AFNetworking, or (more likely), it may be an issue with my code.I've been hacking away for hours trying to solv