Do the files sit connecting for ages before going to 'need more sources'? If they do, they sound like fakes. These things are all over the network now.
Search again, vary your search terms & stay away from files with heaps of sources...go for a file with 10 sources or less, or those with a modem source.

For music files, click on the links below for more info:
How to find music
Info about fake files

For video files, make sure to check the file with Bitzi before download. If a file's been rated, you'll see other users' opinions. Files with lots of sources but no Bitzi rating are likely to be fakes.
How to use Bitzi