Your limewire of course has to send and get messages about the downloads. This isn't http where you get the whole file from one server.

That's why you have to set uploadspeed about 5 KB/s below the max and why you are only getting very slow speeds on video. A videofile is a lot bigger than a music file. This means there are many more messages sent when you download a videofile.

I'm not really in the know of how Gnutella works (the network that Limewire is on) but it is useally a file is made into pieces (the bigger the file the more pieces) which then are split up even more into blocks

Try google or something if you need more info on how Limewire works

If you set your uploadspeed to high then your downloads suffer from it. That's all you really need to know.

BTW speeds are often a bit slower on videofiles, but not that slow