You're probably trying to download fakes. Are they new releases/really popular videos with heaps of sources (up to 100/file)?
Stay away from the files with huge numbers of sources & go for a file with 10 sources or less.

Look up files before download with Bitzi. If users have rated the file, you'll get an idea of it's quality & content. If a file has loads of sources but no Bitzi rating, chances are it's crap.
How to use Bitzi