ktorrent requires an X display to connect to, so it's problematic to run it at startup, as the X display is not connectable to until a user is logged in. If you want instead to start it when you log in, you can use the KDE session system to start it, or create a symlink in your ~/.kde/Autostart folder, like this (run in terminal):
Code:
ln -s $(which ktorrent) "$HOME/.kde/Autostart/ktorrent"