Those 20 minute empty files are are spam/fake, put on the network to disrupt file sharing. There are a lot of them so it could be quite possible to download 50 fake files. More info on that subject here:
Recognising Fake files.
Tips for finding good files here:
How to find music.
Also the limewire player isn't very good and is prone to skipping and cutting out, so try playing files in another player before you scrap them
.