LW is a very poor torrent client. It does not adhere to the requirements of many torrent sites, and therefore cannot dl from some of them (one problem is LW doesn't track share ratios). You will be much better off using a true torrent client, such as Azureus (what I use) or uTorrent (both are free and each has its own advantages).

As to your question re "already downloading" you'll find my answer here:
http://www.gnutellaforums.com/downlo...same-file.html