IMMEDIATELY
Never happens. If Newsbin is downloading 600K chunks of files, it's not going to start another chunk, like your JPG till the 600K chunks in the air complete. That's just how it works. I'm not saying there's no issue, I'm saying that there is no "immediate", there is no interrupt of individual chunks of a file. The file, which might be made of numerous chunks can be interrupted but, it's not an instantaneous thing. It might seem like it but, it's not. The files moved to top don't start downloading till the the chunks of the file currently in process finish.
You may not care about this level of detail but, that's how it works. What I suspect you're seeing is the new cache that lets some chunks get allocated before use and that have to be cycled through before the new topmost gets processed. It's a function of speed and now that I know you have a slow connection, it sort of makes sense to me.
I'll have to think about it. Slow connections take awhile to burn through the cache. Faster connections, you just don't notice it.