There are two possible explanations.

You are trying to download from fake search results or
you are using BearShare 5.2 or 6.

Fake search results are usually uniformly populated with fictional LimeWire
sources with a noticeable randomness to their IP addresses and port numbers.
Click on the little plus sign on the file name to see details on the sources.
Look for files that have a better variety of servent types and check them with
Bitzi before you start downloading. Right-click on any file in BearShare and
the Bitzi ticket command is available.

If you have a crippled version of BearShare (5.2 and up) you can try the one
in this thread instead. http://www.gnutellaforums.com/showthread.php?t=53386