It is important that you understand that ruTorrent is not a bittorrent client
ruTorrent is a web-based user interface (webUI) for rTorrent which is a bittorrent client. rTorrent runs quietly in shell and you do not get to see it most of the time unless you want to. You use your web browser to load ruTorrent — ruTorrent connects to rTorrent behind the scenes and shows you what goes on in rTorrent, your bittorrent client.
Users have reported that torrents can be easily added with a Firefox plugin:
ruTorrent fails to load and gets stuck showing the 'loading' spinner
Clear your browser cache (also known as 'temporary files', not just history), restart your browser and reload ruTorrent, in this particular order.