I understood the question from the beginning!...stop the bickering!! I googled the problem and this thread was at the top of the list! There was another thead which steared me to the solution. This is the fix for firefox:
Tools>Options>Applications>TORRENT File-->Use uTorrent(default)
OK, it's an old thread and I'm a Windows dude but I joined this forum just to say Thank You to jrloader, this has been driving me round the bend for ages - your fix worked a treat.
Once upon a time I would click on a torrent link and it would fire up automatically in uTorrent. Somewhere along the line that got screwed up and for months after that when I clicked on a torrent link the torrent file was downloaded to my desktop and I had to open uTorrent and navigate to the torrent file to open it manually. Now I'm 'back to normal' so Thanks friend