If you are using pro on a cable/dsl connection you should be able to get 10 hosts(I think). If you have a dial up connection the number is less.
Have you found this with many downloads? .. Sometimes there are only 4 hosts available for instance even if the search window shows more.
Also could you just check you DO have pro .. by going to Help or Limewire> about
just to check you did get the correct version from the correct site