Yes, same problem here, when the program starts it says there's no client installed.
I tried the solution that was given, saving a torrent, opening it with Windows Explorer, etc.
Same issue again.
I am using BitSpirit to open torrents, not such a popular one, not sure if this could be the reason.
Fantastic program though, this is the only issue I have with it, otherwise it would be a 5/5 ... 4.5/5 for now. :-)
Thanks to the developer !