Hi marpiw,

If those magnetmix files downloaded very slowly, it might point to your ISP managing bandwidth (throttling) for p2p. Have a look on the Netvision site, check out any terms & conditions. English is my only language, so I can't read any of the info
http://www.netvision.net.il/

Also use Google & search for Netvision throttling p2p, or Netvision p2p...see if you find any info to suggest that Netvision are throttling.

Did you ever try using VLC player to preview movies? Give it a try & see if it works Always check movies with Bitzi before download. If other users have rated the file, you'll get an idea of it's content & quality!
How to use Bitzi