Quote Originally Posted by Budweineken
The "cannot render file" is usually an error that is given when the file is being used by another program, the torrent program might be still using the file so you can't watch it. Pausing and closing the program usually does the trick.
I think all torrent programs allow watching the video even if you are seeding it at the same time. Over at many tracker pages they also recommend you to do that (so that you seed more efficiently).